LightSheer is not bad, but it’s not the best machine around. The absolute best bet for you would be to get a machine that has both alexandrite and yag in one like Apogee Elite or GentleMAX. That way you can treat any skin tones, as long as they have coarse hair of course. Laser doesn’t work on finer hair.
With LightSheer, you’ll still have to turn quite a few people off. You really shouldn’t be treating anyone with skin type darker than IV with it since settings would have to be too low to be effective on anyone darker than that.
There are some websites that sell used machines. There is some mention of them here in past posts if you run a search. Choice on this forum knows of a few such sites I believe. I can’t think of them off the top of my head. You can look on eBay too.