12. Commitments and Contingent Liabilities

We are involved in litigation which may relate to claims brought by governmental authorities, issues with customers, and employment related matters, including class action claims and purported class action claims. As of December 31, 2018, we were not party to any legal proceedings, including class action lawsuits that, individually or in the aggregate, are reasonably expected to have a material adverse effect on our results of operations, financial condition or cash flows. However, the results of these matters cannot be predicted with certainty, and an unfavorable resolution of one or more of these matters could have a material adverse effect on our results of operations, financial condition or cash flows.

We have historically structured our operations so as to minimize ownership of real property. As a result, we lease or sublease substantially all of our facilities. These leases are generally for a period between 5 and 20 years, and are typically structured to include renewal options at our election. We estimate the total undiscounted rent obligations under these leases, including any extension periods that we are reasonably certain to exercise and assuming constant consumer price indices, to be $5.4 billion. Pursuant to the leases for some of our larger facilities, we are required to comply with specified financial ratios, including a “rent coverage” ratio and a debt to EBITDA ratio, each as defined. For these leases, non‑compliance with the ratios may require us to post collateral in the form of a letter of credit. A breach of the other lease covenants gives rise to certain remedies by the landlord, the most severe of which include the termination of the applicable lease and acceleration of the total rent payments due under the lease.

Minimum future rental payments required under operating leases in effect as of December 31, 2018 are as follows:


2019	$	222.5
2020		220.5
2021		217.4
2022		216.0
2023		212.0
2024 and thereafter		4,344.4
	$	5,432.8

Rent expense for the years ended December 31, 2018, 2017, and 2016 amounted to $232.1 million, $225.4 million, and $206.6 million, respectively.

We have sold a number of dealerships to third parties and, as a condition to certain of those sales, remain liable for the lease payments relating to the properties on which those businesses operate in the event of non‑payment by the buyer. We are also party to lease agreements on properties that we no longer use in our retail operations that we have sublet to third parties. We rely on subtenants to pay the rent and maintain the property at these locations. In the event the subtenant does not perform as expected, we may not be able to recover amounts owed to us and we could be required to fulfill these obligations. We believe we have made appropriate reserves relating to these locations. The aggregate rent paid by the tenants on those properties in 2018 was approximately $21.6 million and, in aggregate, we currently guarantee or are otherwise liable for approximately $233.7 million of these lease payments, including lease payments during available renewal periods.

Our floor plan credit agreement with Mercedes Benz Financial Services Australia (“MBA”) provides us revolving loans for the acquisition of commercial vehicles for distribution to our retail network. This facility includes a commitment to repurchase dealer vehicles in the event the dealer’s floor plan agreement with MBA is terminated.

We have $41.4 million of letters of credit outstanding as of December 31, 2018, and have posted $29.2 million of surety bonds in the ordinary course of business.