This is just a shot in the dark, but rather than just flat out walking away yet, have you tried making a revised offer? Tell them that after doing all of your due diligence (inspections, appraisals, etc.) that you cannot go through with the sale at your ORIGINAL OFFERING PRICE - but that if they're still interested in selling you could give them $XXXXX. Chances are, if we're all sitting here telling you this isn't a good deal, it's not going to be a good deal for someone else at that price either.
Sorry to jump in this late but can you lease option it to one of the tenants for $200 more per month?"Hey listen, if I credited you $200 per month toward the purchase price of $xxx,xxxx (YOU set the price) the rent will be $1,500 per month with $200 going as the down payment.If you could set the end price high enough, give them $400 credit for $200 extra paid!