Is paying $15K sellers owe to B/A in a short-sale in my best interest as the buyer?

I've bid on a short-sale home 5 mos. ago. B/A is trying to work with the sellers of the home in which they owe $15K to B/A. My realtor says I have a couple of options as the buyer: I pay 15K & cont. to purchase home or put some cash down and the difference will increase my mortgage loan and monthly mortgage payment. I don't feel it's in my best interest. I welcome other's input.