T.F.
I'm sorry but for a quality set that is a bit unrealistic....UNLESS.....you find someone that has a good set that wants to get rid of it.
We have a Woodlawn we bought in 2000 and it still looks new. We paid about $2500 for it (we did get some extras)and it has held up very well. The dealer installed and leveled it. We've never had an issue with it. It is hardly used now because our daughter is now 14. When it is used, they are usually on top of it somehow vs using the swings.
Rainbow and Wooden Swing are also good quality companies.
If $500 is your budget, I would look for a used set on Craigslist where you go take it apart, move it and take it home.
My advice is to buy the best quality you can afford. You do get what you pay for and if you go cheap, you'll be buying another set a couple years down the road.
Good luck!!