Hey-o!
Yeah, I tend to agree with Van_Dweller when he mentions the Craigslist/Older RV option.
I’m literally at the end of my build, which has taken me a year (6 months longer than I planned / intended) and probably about $20000+ in so far?
I bought it hook, line, and sinker from the Youtube Influencers / Prepper community. I’ve got the beefy solar setup, the 4 giant 800ah battery bank, the recirculating shower system, blah blah blah…
Not to mention the mistakes. Oh, my mistakes were many, and many were costly. I literally bought an entire shower stall (a cheap one at like $500). But after cutting and recutting, thinking I could make it work, finally I realized there was just no way and LITERALLY threw the thing out after I had cut it into all sorts of funky shapes. I literally threw $500 in the trash.
I should have bought a camper for $3500 about 10 months back, and saved the other $16,500 for the piece of farm property I want in a few years.
I know the Youtube Vans look super cool, and they look super cute, but they really aren’t worth it unless…
1 - You specifically want to gain experience in building/converting Vans/Shuttles.
2 - You want to sink a bunch of money into your mistakes.
3 - You want something very specific, like an extreme off-grid capable vehicle.
4 - Because you only live once so why not!
But seriously, I don’t regret my build or all the awesome things I’ve learned along the way. However, my goal was to travel and save money doing so. Instead, I’ve spent the last year building my Shuttle, and spent ZERO time traveling or saving money. 
Like Van_Dweller said, not trying to be a downer or discourage you from a super awesome build. Just want to prepare you for the bad of a self build when not a professional, like being influenced or making mistakes. If none of that deters you, and knowing you are going to waste money doing this is okay so long as you gain it back in experience, then jump on in! 
If those things don’t bother you though, I still wouldn’t buy a new vehicle and finance it. There are a ton of used options out there that are just as good, if not better.