I have found stuff on Craigslist and ebay. If you google the item you are looking for, you should come up with dealers and used dealers of it. As Karin mentioned, I would stay with commercial grade equipment for the cardio (vs home equipment). If you can find a cardio piece that is commercial grade and has been in someone’s house, that will obviously have a lot less use on it. A nice trick for moving pieces and equipment around is four wheel dollys that you can buy at a Home Depot, Harbor Frieght Tools, etc.