Originally Posted by Erwin8r

I'll also add my vote for a used, 90's steel mountain bike. I remember reading about people on this forum at 450+ lbs riding steel rigid mountain bikes (trek, specialized, etc)--And many with amazing results! Even if you spent $250 and another $200 on beefed-up wheels, you'd be on a safe, proven bike at well under your budget.

The best thing you can do is to just get started--somehow, someway, take that first step. Bring all your questions here and you'll find many will chime in to help. Good luck!