To clarify, modern VA loans do, in fact, have due on sale clauses. If an owner simply signs-over the deed to his property to a new owner, the loan can be called due. However, if the property is sold on contract for deed to a new owner, the loan cannot be called due.
Anthony, you might check on these dates, but FHA mortgages originated before December 15, 1989 and VA mortgages originated before March 1, 1988 do not require the approval of the lender for them to be assumed by someone other than the original mortgagor. After these dates, they became assumable with qualifying. That is, you had to get the lender’s permission to transfer the loan to someone else, or risk that it might be called due.
These older loans are decreasing in number every day as they are paid off or refinanced.