Cheapest way to build basement walls?

I would change the color of the bed sheets then. Just kidding....You are only going to create another remodeling project if you don't at least put up some studs and dry wall. Remember anything done that is not right will only cost you time and money later. But if time and/or cost is an issue, and what I have done in the past, is go to home depot and buy heavy duty paint drop clothes and use as a divider. They are pretty big and you can secure them pretty tight so it does look like a wall. You can even paint them if you want.