I can't offer a suggestion specifically on steel, but I started with a Diamondback Wildewood Deluxe mountain bike (aluminum). I think it was 2003. I was about $400 if I recall. I weighed in at about 385 when I started.

I do highly recommend you invest in the tools and a book on truing your own wheels. It didn't take to many rides before I had wacked mine out pretty good. I trued them then a few times and they have been good since.