NOTE 10. RENTAL INCOME

During the six months ended June 30, 2019, approximately 94% of rental income was related to residential apartments and condominium units with leases of one year or less. The majority of these leases expire in June, July and August. Approximately 6% was related to commercial properties, which have minimum future annual rental income on non-cancellable operating leases at June 30, 2019 as follows:


	Commercial
	Property Leases
2020	$	2,799,000
2021		2,595,000
2022		1,674,000
2023		1,229,000
2024		698,000
Thereafter		742,000
	$	9,737,000

The aggregate minimum future rental income does not include contingent rentals that may be received under various leases in connection with common area charges and real estate taxes. Aggregate contingent rentals from continuing operations were approximately $277,000 and $449,000 for the six months ended June 30, 2019 and 2018 respectively. Staples and Trader Joes, tenants at Staples Plaza, are approximately 31% of the total commercial rental income.

The following information is provided for commercial leases:


	Annual base				Percentage of
	rent for		Total square feet	Total number of	annual base rent for
Through June 30,	expiring leases		for expiring leases	leases expiring	expiring leases
2020	$	164,818	9,262	8	6	%
2021		747,156	28,897	9	25	%
2022		605,588	24,225	8	20	%
2023		472,907	13,151	7	16	%
2024		484,028	14,668	8	17	%
2025		308,905	12,630	4	11	%
2026		—	—	—	—	%
2027		—	—	—	—	%
2028		—	—	—	—	%
2029		—	—	—	—	%
2030		142,450	3,850	1	5	%
Totals	$	2,925,852	106,683	45	100	%

Rents receivable are net of an allowance for doubtful accounts of approximately $324,000 and $532,000 at June 30, 2019 and December 31, 2018. Included in rents receivable at June 30, 2019 is approximately $90,000 resulting from recognizing rental income from non-cancelable commercial leases with future rental increases on a straight-line basis. The majority of this amount is for long-term leases at 62 Boylston Street and Staples Plaza in Massachusetts.

Rents receivable at June 30, 2019 also includes approximately $69,000 representing the deferral of rental concession primarily related to the residential properties.