Can I use a preowned Tivo that I bought at a thrift store?

Hello all! I see Tivos all the time at thrift stores. I know Tivo has a subscription service, but can I buy one of these used Tivos and call the company and get set up? I don't want to buy one that was leased from say Dish Network or something and have a "hot Tivo" on my hands because it was not turned in. Is there a way to make sure the box I buy used is useful? Thanks for any help!