At the beginning, I didn't know exactly what model of van I wanted, but one thing was clear to me: I didn't want a very big one. Being my first camper, I wanted something small (but not too small) and manageable. Besides, at the moment I live in a big city, and I didn't want a mastodon that I couldn't park anywhere.
That already limited the options. But I had another important criterion. I'm going to invest a lot of money, time and effort in this van. In other words, I want it to last. I don't want a tin can that I have to tighten the bolts every thousand km, or that will leave me stranded after 50,000.
After looking at a few models, I settled on the Mercedes Vito. Ok, they are a bit more expensive, but Mercedes usually last longer. I have an acquaintance who has had many camper vans in his life and has stretched the Vito to 600,000 km. And besides, it's nice.

And finally, I wanted something under 150,000 km, and not too old either (around 10 years old). For the same reason as two paragraphs ago: I want it to last. And also, I wanted it to be worth between 10 and 15 thousand euros. With the way prices are lately, this was not quite realistic. But he who seeks, finds, which brings me to the next section.
If you have ever bought a second hand car (or anything really), you will already know how many options you can get. I found it difficult to compare several offers with 16,000 tabs open in the browser, so I made myself a little program to "scrape" several Spanish and German second hand sales pages.

First version of the mini-app to search for furgos.
At the moment I leave the list of pages and applications I visited:
Quite simply: I took out a loan. Once I found a few vans that fit those criteria, I took advantage of a bank offer and asked for 14,000€. I guess with that, part of my salary, and some of my savings I will be able to complete the purchase and the camperization.
There is one thing I haven't told you yet. When I was thinking about buying the van, my sister was working and living in Berlin. All advantages: