If you’re on a tight budget, buying a used engine might be a good way to save money. Most of them come with engine logbooks so you know their history. Some of these used engines are prop strikes that are only a few hours old. Many used engine sellers will put a 30 day warranty on them. But remember, removal and reinstallation is a big expense (up to $6k) so a good deal on a half-timed engine might not be as good of a deal if you add in that cost.
Buying a used engine after yours runs out is more common with turbines than piston engines.