Is a second-hand cat tree a sensible budget option?

It can be, but condition, cleanliness and access to the original specifications matter. Inspect every joint, platform, post and attachment rather than judging only the visible fabric. Ask about damage, repairs, missing parts and the model's instructions or load limits. Worn upholstery may be replaceable, but structural damage is a different issue. Consider whether the item can be cleaned appropriately and whether any previous animal health concerns affect your decision. A cheap purchase can become costly if essential parts are unavailable or transport is difficult.

Do not use improvised replacement fittings without knowing they are suitable. If you cannot establish that the tree is safe for your cat, walk away. Buying second-hand should reduce waste and cost while retaining the basic requirements of a secure, usable product; uncertainty about its structure is not a bargain. Request clear photographs of the underside, base and joints before arranging collection, then inspect them in person rather than relying solely on the listing.