i did this job, full time for about 3 years, it was fun. you get to meet some really cool people. You basically work when you want. The downside is business gets slow and you might not have work so i would only recommend doing this part time, or on the side. local shops around here basically choked me out with their better pricing. working for icracked you HAVE to use their parts and their parts are pretty expensive which causes your prices to generally be higher. another downsid is having to do warranty repairs for customers. you are compensated for the warranty (parts only) but its a long process and generally just sucks to deal with. It's a risky business but if you have the money to invest in it and want a side job then go for it. You use your own car / your own gas and you buy your own parts and tools.
Make your own schedule. Meet cool people
Buy your own parts. Wear and tear on your vehicle. Warranty repairs.