Billy Dent, as the owner of an apartment building, receives and makes the following payments during 2010:
Received in January 2010 rent that was due in December 2009 ...... $5,000
Received in December 2010 rent not due until January 2011 ........ 4,000
Security deposit which is to be refunded when tenant vacates the apartment.................. 500
How much rental income must Billy Dent include on his 2010 income tax return?