At that price range, frankly, you're looking for secondhand. Couches are ridiculously overpriced. But you can make that work for you.
Consider making or purchasing slipcovers (lots available online), and possibly attaching wheels yourself. Use screws, not nails, and you'll be fine. You may need to shorten the legs if the wheels raise it too high, so you're looking for something with simple wooden legs, not fancy claw feet.