If you bought a suit that was stated to be "100% ready to go" and your only choice was to trust that was the case and later ate the loss when it wasn’t, that’s unfortunate. But a mistake was made to have used a method where you couldn’t hold the seller accountable.
There are lots of great used suits out there. A 20 year old DUI can easily give 1000’s more dives (With replacement of wear components). But it’s definitely buyer beware. Buy from someone you trust, or somewhere you can get a warranty like eBay. Lastly, get an opinion from someone with more experience before investing in a used suit. Comments above about being comfortable with making minor repairs (replacing seals) is well placed. I would say this goes for any drysuit diver on a tight budget, regardless of whether bought new or used. Seals are wear items, expensive to have someone else replace, especially if it requires mailing.
good luck