I definitely think that building it yourself is the way to go as well! I have a lot of gear and stuff since I'm living in it full-time and don't have any other storage, so I needed to build mine specifically for my needs. I wouldn't have been able to do that in a conversion van. I did go with a brand new van though (after a huge loss from buying an old Sprinter off of Craigslist) and I'm happy to not have to worry about the van itself having any mechanical issues. I think my buildout probably cost $6,000 or so. Should have kept track of my spending on it!