Sandwich Lease option question?

I have a sandwich lease option set up. I'm up $2800 so far and haven't really done much. The tenant is talking about exercising his option to purchase. The problem I've been running into is I can't find a mortgage company/lender to lend him the money because they say I don't own the place and refuse to loan him the money. Does anyone out there use a certain bank for sandwich lease options?