﻿<?xml version="1.0" encoding="utf-8"?>
<InstanceReport xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Version>2.2.0.7</Version>
  <hasSegments>false</hasSegments>
  <ReportName>Business</ReportName>
  <ReportLongName>0201 - Disclosure - Business</ReportLongName>
  <DisplayLabelColumn>true</DisplayLabelColumn>
  <ShowElementNames>false</ShowElementNames>
  <RoundingOption />
  <HasEmbeddedReports>false</HasEmbeddedReports>
  <Columns>
    <Column>
      <LabelColumn>false</LabelColumn>
      <Id>1</Id>
      <Labels>
        <Label Id="1" Label="6 Months Ended" />
        <Label Id="2" Label="Jun. 30, 2010" />
      </Labels>
      <CurrencyCode>USD</CurrencyCode>
      <FootnoteIndexer />
      <hasSegments>false</hasSegments>
      <hasScenarios>false</hasScenarios>
      <Segments />
      <Scenarios />
      <Units>
        <Unit>
          <UnitID>USD</UnitID>
          <UnitType>Standard</UnitType>
          <StandardMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/iso4217</MeasureSchema>
            <MeasureValue>USD</MeasureValue>
            <MeasureNamespace>iso4217</MeasureNamespace>
          </StandardMeasure>
          <Scale>0</Scale>
        </Unit>
        <Unit>
          <UnitID>USDEPS</UnitID>
          <UnitType>Divide</UnitType>
          <NumeratorMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/iso4217</MeasureSchema>
            <MeasureValue>USD</MeasureValue>
            <MeasureNamespace>iso4217</MeasureNamespace>
          </NumeratorMeasure>
          <DenominatorMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/instance</MeasureSchema>
            <MeasureValue>shares</MeasureValue>
            <MeasureNamespace>xbrli</MeasureNamespace>
          </DenominatorMeasure>
          <Scale>0</Scale>
        </Unit>
        <Unit>
          <UnitID>Shares</UnitID>
          <UnitType>Standard</UnitType>
          <StandardMeasure>
            <MeasureSchema>http://www.xbrl.org/2003/instance</MeasureSchema>
            <MeasureValue>shares</MeasureValue>
            <MeasureNamespace>xbrli</MeasureNamespace>
          </StandardMeasure>
          <Scale>0</Scale>
        </Unit>
      </Units>
      <CurrencySymbol>$</CurrencySymbol>
    </Column>
  </Columns>
  <Rows>
    <Row>
      <Id>2</Id>
      <Label>Business [Abstract]</Label>
      <Level>0</Level>
      <ElementName>wpc_BusinessAbstract</ElementName>
      <ElementPrefix>wpc</ElementPrefix>
      <IsBaseElement>false</IsBaseElement>
      <BalanceType>na</BalanceType>
      <PeriodType>duration</PeriodType>
      <ShortDefinition>Business.</ShortDefinition>
      <IsReportTitle>false</IsReportTitle>
      <IsSegmentTitle>false</IsSegmentTitle>
      <IsSubReportEnd>false</IsSubReportEnd>
      <IsCalendarTitle>false</IsCalendarTitle>
      <IsTuple>false</IsTuple>
      <IsAbstractGroupTitle>true</IsAbstractGroupTitle>
      <IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow>
      <IsEquityAdjustmentRow>false</IsEquityAdjustmentRow>
      <IsBeginningBalance>false</IsBeginningBalance>
      <IsEndingBalance>false</IsEndingBalance>
      <IsReverseSign>false</IsReverseSign>
      <PreferredLabelRole />
      <IsEPS>false</IsEPS>
      <FootnoteIndexer />
      <Cells>
        <Cell>
          <Id>1</Id>
          <ShowCurrencySymbol>false</ShowCurrencySymbol>
          <IsNumeric>false</IsNumeric>
          <IsRatio>false</IsRatio>
          <DisplayZeroAsNone>false</DisplayZeroAsNone>
          <NumericAmount>0</NumericAmount>
          <RoundedNumericAmount>0</RoundedNumericAmount>
          <NonNumbericText />
          <NonNumericTextHeader />
          <FootnoteIndexer />
          <hasSegments>false</hasSegments>
          <hasScenarios>false</hasScenarios>
          <DisplayDateInUSFormat>false</DisplayDateInUSFormat>
        </Cell>
      </Cells>
      <OriginalInstanceReportColumns />
      <ElementDataType>xbrli:stringItemType</ElementDataType>
      <SimpleDataType>string</SimpleDataType>
      <ElementDefenition>Business.</ElementDefenition>
      <IsTotalLabel>false</IsTotalLabel>
    </Row>
    <Row>
      <Id>3</Id>
      <Label>Business</Label>
      <Level>1</Level>
      <ElementName>us-gaap_NatureOfOperations</ElementName>
      <ElementPrefix>us-gaap</ElementPrefix>
      <IsBaseElement>true</IsBaseElement>
      <BalanceType>na</BalanceType>
      <PeriodType>duration</PeriodType>
      <ShortDefinition>No definition available.</ShortDefinition>
      <IsReportTitle>false</IsReportTitle>
      <IsSegmentTitle>false</IsSegmentTitle>
      <IsSubReportEnd>false</IsSubReportEnd>
      <IsCalendarTitle>false</IsCalendarTitle>
      <IsTuple>false</IsTuple>
      <IsAbstractGroupTitle>false</IsAbstractGroupTitle>
      <IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow>
      <IsEquityAdjustmentRow>false</IsEquityAdjustmentRow>
      <IsBeginningBalance>false</IsBeginningBalance>
      <IsEndingBalance>false</IsEndingBalance>
      <IsReverseSign>false</IsReverseSign>
      <PreferredLabelRole>verboselabel</PreferredLabelRole>
      <IsEPS>false</IsEPS>
      <FootnoteIndexer />
      <Cells>
        <Cell>
          <Id>1</Id>
          <ShowCurrencySymbol>false</ShowCurrencySymbol>
          <IsNumeric>false</IsNumeric>
          <IsRatio>false</IsRatio>
          <DisplayZeroAsNone>false</DisplayZeroAsNone>
          <NumericAmount>0</NumericAmount>
          <RoundedNumericAmount>0</RoundedNumericAmount>
          <NonNumbericText>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;
   &lt;!-- Begin Block Tagged Note 1 - us-gaap:NatureOfOperations--&gt;
   &lt;div align="left" style="font-family: 'Times New Roman',Times,serif; margin-left: 0in; "&gt;
   &lt;!-- xbrl,ns --&gt;
   &lt;!-- xbrl,nx --&gt;
   &lt;div align="left"&gt;
   &lt;/div&gt;
   &lt;div align="center" style="font-size: 10pt; margin-top: 0pt"&gt;&lt;b&gt;
   &lt;/b&gt;&lt;/div&gt;
   &lt;div align="center" style="font-size: 10pt; margin-top: 0pt"&gt;&lt;b&gt;&lt;/b&gt;
   &lt;/div&gt;
   &lt;div align="left" style="font-size: 10pt; margin-top: 10pt"&gt;&lt;b&gt;Note 1. Business&lt;/b&gt;
   &lt;/div&gt;
   &lt;div align="left" style="font-size: 10pt; margin-top: 10pt"&gt;W. P. Carey &amp;#038; Co. LLC (&amp;#8220;W. P. Carey&amp;#8221; and, together with its consolidated subsidiaries and
   predecessors, &amp;#8220;we&amp;#8221;, &amp;#8220;us&amp;#8221; or &amp;#8220;our&amp;#8221;) provides long-term financing via sale-leaseback and
   build-to-suit transactions for companies worldwide and manages a global investment portfolio. We
   invest primarily in commercial properties domestically and internationally that are each triple-net
   leased to single corporate tenants, which requires each tenant to pay substantially all of the
   costs associated with operating and maintaining the property. We also earn revenue as the advisor
   to publicly owned, non-listed real estate investment trusts, which are sponsored by us under the
   Corporate Property Associates brand name (the &amp;#8220;CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt; REITs&amp;#8221;) and invest in
   similar properties. We are currently the advisor to the following CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt; REITs:
   Corporate Property Associates 14 Incorporated (&amp;#8220;CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt;:14&amp;#8221;), Corporate Property
   Associates 15 Incorporated (&amp;#8220;CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt;:15&amp;#8221;), Corporate Property Associates 16 &amp;#8212;
   Global Incorporated (&amp;#8220;CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt;:16 &amp;#8212; Global&amp;#8221;) and Corporate Property Associates
   17 &amp;#8212; Global Incorporated (&amp;#8220;CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt;:17 &amp;#8212; Global&amp;#8221;). At June&amp;#160;30, 2010, we owned
   and managed 922 properties domestically and internationally. Our own portfolio was comprised of our
   full or partial ownership interest in 167 properties, substantially all of which were net leased to
   80 tenants, and totaled approximately 14&amp;#160;million square feet (on a pro rata basis) with an
   occupancy rate of approximately 92%.
   &lt;/div&gt;
   &lt;div align="left" style="font-size: 10pt; margin-top: 10pt"&gt;&lt;b&gt;Primary Business Segments&lt;/b&gt;
   &lt;/div&gt;
   &lt;div align="left" style="font-size: 10pt; margin-top: 10pt"&gt;&lt;i&gt;Investment Management &lt;/i&gt;&amp;#8212; We structure and negotiate investments and debt placement transactions for
   the CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt; REITs, for which we earn structuring revenue, and manage their portfolios of
   real estate investments, for which we earn asset-based management and performance revenue. We earn
   asset-based management and performance revenue from the CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt; REITs based on the value of
   their real estate-related assets under management. As funds available to the CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt; REITs
   are invested, the asset base from which we earn revenue increases. In addition, we also receive a
   percentage of distributions of available cash from CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt;:17 &amp;#8212; Global&amp;#8217;s operating
   partnership. We may also earn incentive and disposition revenue and receive other compensation in
   connection with providing liquidity alternatives to CPA&lt;sup style="font-size: 85%; vertical-align: text-top"&gt;&amp;#174;&lt;/sup&gt; REIT shareholders.
   &lt;/div&gt;
   &lt;div align="left" style="font-size: 10pt; margin-top: 10pt"&gt;&lt;i&gt;Real Estate Ownership &lt;/i&gt;&amp;#8212; We own and invest in commercial properties in the United States of America
   (&amp;#8220;U.S.&amp;#8221;) and the European Union that are then leased to companies, primarily on a triple-net leased
   basis. We may also invest in other properties if opportunities arise.
   &lt;/div&gt;
   &lt;/div&gt;
</NonNumbericText>
          <NonNumericTextHeader>&lt;!--DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" --&gt;
   &lt;!-- Begin Block Tagged Note</NonNumericTextHeader>
          <FootnoteIndexer />
          <hasSegments>false</hasSegments>
          <hasScenarios>false</hasScenarios>
          <DisplayDateInUSFormat>false</DisplayDateInUSFormat>
        </Cell>
      </Cells>
      <OriginalInstanceReportColumns />
      <ElementDataType>us-types:textBlockItemType</ElementDataType>
      <SimpleDataType>textblock</SimpleDataType>
      <ElementDefenition>Describes the nature of an entity's business, the major products or services it sells or provides and its principal markets, including the locations of those markets. If the entity operates in more than one business, the disclosure also indicates the relative importance of its operations in each business and the basis for the determination (for example, assets, revenues, or earnings). Disclosures about the nature of operations need not be quantified; relative importance could be conveyed by use of terms such as "predominately", "about equally", or "major and other". This element is also referred to as "Business Description".</ElementDefenition>
      <ElementReferences>Reference 1: http://www.xbrl.org/2003/role/presentationRef
 -Publisher AICPA
 -Name Statement of Position (SOP)
 -Number 94-6
 -Paragraph 10

</ElementReferences>
      <IsTotalLabel>false</IsTotalLabel>
    </Row>
  </Rows>
  <Footnotes />
  <NumberOfCols>1</NumberOfCols>
  <NumberOfRows>2</NumberOfRows>
  <HasScenarios>false</HasScenarios>
  <MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel>
  <SharesRoundingLevel>UnKnown</SharesRoundingLevel>
  <PerShareRoundingLevel>UnKnown</PerShareRoundingLevel>
  <HasPureData>false</HasPureData>
  <SharesShouldBeRounded>true</SharesShouldBeRounded>
</InstanceReport>
