Oh I see. You are looking to do this at home? I guess I still don't exactly get your use case. If you are saying you want a TV in a room that you will use as a TV but also to do some productivity work, then at the distance you describe, I would say 65". Even then, I would try to test it out. I am not sure how easy it would be to see text at that distance, even on a 65".
If you are thinking of just being able to do work on a couch, would a 12.9" iPad Pro do the trick?