Subject To - Reluctant Banker

Hi Guys,

I'm working on a Subject To deal but the seller is being blocked by recalcitrant lender.  The seller has a 230K mortgage on the house that I'm trying to take over subject to. He is moving to a new smaller house but is having some trouble getting prequalified by the lender. His credit is okay, about 600. We're shopping for the new house and want to get him preapproved for financing.  The lender says he cannot have two loans under his name, not with his income. He needs to sell the house first.  My contention is that I will be covering his payments. What's the best way of communicating this with the lender?  Should I buy the house first subject to, rent it back to the seller, then try to get preapproved?  How do you get the lender to understand the subject to concept?

Jason