Hi Jessy, this is the second time I've written this reply (apparently my first reply took too long and I had to re-log in) so apologies if this is a bit abrupt. Good news is it's fresh in my mind so hopefully I can write faster and leaner.
We bought a T4 Westfalia Volkswagon ('95) within a week of us agreeing a van was the best option; Armando spotting it and meeting the owner; and the owner selling it that week. We paid around 6,000 Euros for what's known as a 'pre-made' in some odd vanlife circles. We have a fridge/stovetop/sink and pullout bed plus pop top.
We were super lucky.
It depends on what you want, though. We met a fella from the UK on the road in Morocco and he'd spent (I think-?) around £2,000 for a van skeleton and around £11,000 for the conversion to where he was happy. For us the priority was to travel together, comfortably; for him, it was to make a home. It took him several months, so that's a commitment - but he does have a really beautiful place in his van.
I'll make this short in case I get cut off again. I'd sent links earlier, but basically when you look use keywords like: buy campervan in X (US/UK/CZ (where we bought ours)) or van for sale in X. Switch up the keywords. Have fun with it-! Also, ask around. Someone might know someone with a van. And ask on groups. I dunno how many FB groups you've checked out, but ask on sites designed to find owners for sellers - specifically for vans.
Hope this is helpful, let me know whatever other info you need.