Hi Kathy,
Hello from Huntsville, AL. Not in TX, but assumable loan opportunities are pretty much the same everywhere. For several years now, lenders with which I am working no longer allow the assumption of a mortgage. So as homes change hands and new mortgages are created, there are now very, very few if any houses for sale which would have assumable loans.
There are exceptions. I think VA still can be assumed, and if a seller allows a purchaser to assume that loan, then the seller is still responsible for that mortgage. So most are not willing to allow someone else to assume their loan.
I am a real estate broker and not a lender. You should check with a local lender to get their comments on assumable loans as they deal with it everyday.