With a used RV regardless of manufacturer it's all about how it was kept, and the condition it is in.
Bigfoots are well made, but that is in RV terms. The biggest thing to look for is functioning systems and water damage. Both get expensive very quickly.
From what we have seen lots of Bigfoot owners keep their rigs for a while. Ours was owned by the first owner for 16 years before we bought it. And they have a decently high resale value assuming
leaks are prevented or repaired and systems are functional.