I'm going to assume your referring to a blanket mortgage, or maybe a bridge loan. Let me see if I have this right.
You want to get one mortgage that has 2 houses as the collateral. And then get a 2nd mortgage, also a blanket mortgage on the same 2 houses? If that's what your wanting to do, I've never ran across it before from a GSA or local bank stand point. (Not that it doesn't exist, it could) I know of no reason that it couldn't be done. It's just trying to find the lender who will do it.