Tador, awesome back story, I was in a similar boat as you up until about 4 years ago (39 now). I was always fascinated with the Trx250r even though I kept ending up with other bikes (rm85 at 14 years old onto a kx125, ktm125, 250x, LT500r, LT250r, Tecate-4, Z400, 350x) Then finally got a Trx250r about 4 years ago - sold it like a fool, then built another from scratch - sold that like a fool, then built my Laeger - that I have posted for sale like a fool but at top dollar (I have problems, emotionally self destructive)....
NOTHING beats the Trx250r..... The strange amazing Ora they give off just by looking at them is one thing! But they also ride and handle amazing when fresh.
If you don't have the beans to drop on a solid one, I would suggest buying a Frame and purchasing part by part using this forum for advice!! You will learn so much, know the bike inside out, and become an educator to those with dropped jaws when you go out riding. Or find one that's clapped out to rebuild (cheaper in the long run)
Stock frames roughly $300 and aftermarket used roughly $1000 (I would suggest aftermarket if you can, if not, no biggie really). Plus it's a fun adventure searching parts which I still do it today although I'm not buying (remember, I have problems).