If you're going to obtain financing, and can wait to move in....your only option would be to purchase it as an investment property and pay 20% down. You wouldn't be able to use the rental income to qualify and you would need to have enough funds to cover closing (down payment and closing costs) , 2 months reserves for your current housing, and 2 months reserves for the new apartment payment.
Otherwise, like Alysse and Kerry stated, you'll need to keep looking until you find a vacant apartment.
If I can help you with financing options and/or questions, please feel free to call me.
Vino Alonzo, Loan Officer
First Cal Mortgage
Kerry Redding, Realtor
Visit me on the web! http://CedarParkDreamHomes.com