I got my bike through facebook. There's a part of Facebook called "Marketplace" where people sell items like furniture, exercise equipment, cars, etc. I don't know if it's an international feature. I've found it quite handy though. A radius of how many miles around my location can be set, so that only items in range of how far I'm willing to drive appear in the search. I've seen a couple weight lifting machines listed for around $100-150 too, and plan on getting one if/when my hip/tailbone situation improves.
I always do searches for reviews the equipment - which can almost always be found on Amazon - as well as the original cost, to help me determine which used equipment is a good deal. If there are at least a couple reviews that said the product wasn't solidly made or didn't move smoothly, I'd pass.
I've seen that here, most of the stuff listed is stuff I'm not interested in and it has a certain character, like a lot of the pawn shops or hawking shops like CEX here.
Although I could see it being useful, I know someone who simply left a big multi gym weight suite in a house because they were moving home and did not have the guide in order to disassemble it. They were worried that the people moving in would eventually contact them and tell them to get it removed. It was in the garage with a rowing machine and recumbent bike that they did get sold.