That will work, but you'll have to respace and redish the wheel to get a proper chainline on it. You'll have to do that no matter what unless you find a cheap freehub/cassette wheel and get a cog to put on it.

The cheapest way would be to go to your LBS or local bike graveyard and find a freewheel rear wheel. You'll still have to respace and redish, but it shouldn't be any harder than that Formula one.