What kind of stand would we need to build for a swing if we have no trees?

the cheapest way would probably be to try and find an old swingset at a yardsale or post a want ad on yahoo groups. lots of time when the slide or swing seats break people just get rid of them by throwing them away and buy a new one. but the frame is still good to put something like a tire swing on. of course they won't be able to swing as wide as with a good tall tree, but it's a suggestion. good luck