As mentioned above, having the proper insurance would not only help you get customers, but may save you someday if something goes wrong. As far as if there is a market? Depending on your cost and area, I would think it's possible. I don't know about full time, but maybe part-time work. There are a few stump grinder guys around Kansas City that only do stump grinding and nothing else. Granted those guys normally have larger stump grinders that a local tree company may not have so that's why they get hired, but I've worked for a guy that despite having a couple good stump grinders, he prefered to outsource that work. In the past when I used to do a lot of side jobs on the weekends, I would pass up jobs because I knew I wouldn't have the time or the energy to do both the take down and clean up. I can see getting some work out of small outfits or tree guys that do side jobs on the weekends, but I don't know about getting much work full time from a large tree company. Eitherway, good luck.