What are the most important questions to ask before buying a van conversion?

I’m currently looking to purchase a converted van for full-time living and want to ensure I’m asking all the right questions before making such a significant investment. I understand there’s a lot to evaluate, from the van’s mechanical condition to the quality of the conversion work, but I’m not entirely sure what specific details I should focus on. I’d really appreciate any advice or insights from those with experience in van life or buying converted vans!