You get a projector and get a screen that small. Most do a 120" minimum even with a crappy one.
I got a decent one and put a 100" pull down in the living room. The projector will do up to a 300". I bought a blow up 28' screen from amazon for $150 and haven't used it yet but I'm anticipating the awesomeness.
Your own drive in theater. My projector only does 1080. That's how you get one for $300 that can do 300" screen.
I would consider a 100" pull down. Can link the one I bought.