Once a homeowner sells their home sub2 to an investor, do they have legal recourse down the road (a year or two) if the mortgage isn’t refinanced out of their name?
Unless you have put into writing that you will refi within a specific period of time, no, the seller has no recourse.
The seller sold the house to you subject to the liens that were in place. You make the payments on time as you should. Pay it off on your time frame.