I did very well. I'd pick up mowers from many different places. Some customers had extra's they didn't want anymore. Sometimes when I was in the scrap yard, I'd see nice looking mowers that only needed a few things. (lot of those in the scrap yard). Put maybe $100 into it and sell it for $500 or $600.
As far as warranty goes, I'd give a 30 day warranty on ONLY what I repaired. Everything else was as is. And most times, I'd have a list of what I warrantied for 30 days.
When I started out, that's all I did. Then word got around and people started bringing me stuff to fix. It was then that I started getting so bogged down in repairs, that I was working night and day just trying to keep up with repairs.