Greetings & Welcome!
The problem with new or newish vans, that areen’t fully depreciated is that they will quickly and continually lose value until they are fully depreciated. Additionally, non factory, non RVIA certified camper conversions rarely raise the value of the vehicle, and can cause insurance hassles ass well.
Given my choice, I would choose a cheap older factory RV first, followed by a cheap older factory camper van, and self conversions last, and vans as the last choice in those since they’re the smallest. That being said, I have done just about everything except airplanes, including boats, over the last 50 years. For the last 11 years, I’ve been in a 1973 high top Dodge Maxi Van that was gutted when I purchased it for $700. ~$300 later, it was move in ready.
After doing many, many builds both for myself, and for other people, I have come to the conclusion that “no build” builds are the best. Most passenger vans & buses have factory finished floors, walls, & ceilings. With buses, I’ll lay carpet over the rubber floors. Once the seats are removed, you can just move your new interior in and secure it, rather than building it in. Almost everything can be found for free or dirt cheap, and it doesn’t mean sacrificing anything. I have everything an expensive RV would have, except a microwave, because I couldn’t justify the space used for how little I use them. I also try to avoid things that are power hungry, opting for fuel powered amenities as well.
I would say it generally takes me about a week to locate & pick up everything I want or need. I will often just move it in and secure it as soon as it is picked up and loaded. If I know I’ll be building one soon, I will gather everything first, then it will only take a few hours to move everything in and secure it. Keeping everything portable and modular has great advantages over built ins. Even my isolator has a quick disconnect on it, to make my power system portable too.
"The secret to success: LOW BUDGET EVERYTHING!" ~ MoneySavers