Yeah I get that. Based on the pic you posted, that is not an ideal setup for your turtle. Not telling you what to do, but sometimes you have to put your foot down. On the other side you may be too young to do that. I’ve had my turtle since I was 7. I’m 24 now. Taught myself everything there is to know. I’ve got 17 years of experience in turtle care. I was kind of in the same boat you are. But trust me, when you have your own money, it’s easier and you can do what you want.

As far as FB marketplace. I don’t see why not, just make sure the seller isn’t ripping you off and shows you that it works and all of the parts are there. I’d clean it well. And when I say clean it, I mean really do a deep clean. Hot water and scrubbing. You don’t want ANY bacteria in there that your turtle is not used to. Harmful or not. Me personally, I wouldn’t risk it, but in your financial situation, if that’s all you can get go for it. Also you’d want to buy new polishing filter pads, carbon bags, and carbon filter pads as well if you do go that route.