Tools, damned expensive, I hate to think of what I have in my shop, but probably around $50K in tools all together. There's nothing wrong with Craftsman, don't by into the Matco, Snap-on, Mac hype. Also look closely at S-K tools!!!
IMO the real money is in RV's and Diesels and the combination of both. First off your dealing with customers that have money. Second the jobs take alot of time. Troubleshooting electrical, lights, A/C, plumbing, water tanks, grey water, black water, axles, bearings, etc. etc. Not to mention the new diesel pushers and the service that goes with those and the diesel gensets. If you want to make some $$$ look for a small shop with an owner you like that does towing and repair or do your own down the road, places like small RV parks. People (RV'ers) are more likely to have you fix it than tow it or drive it many miles to a dealership. And they pay in cash or travelers checks. Work as a 50%'er, I was able to pull down over 1K per week at the place I worked at driving semi-tow trucks and fixing RV's.
One time I towed in a new RV that the DOT stopped for leaking water on the road. It was a leak under the sink area that was running down through a hole in the floor onto the highway. $400 tow bill and $50 repair where the factory had forgotton to hook up a drain pipe to the tank!!! The owner was PO'd, but I got a $200 tip, just for being nice and fixing it right away so he didn't have to get towed another 150 miles to an authorized repair facility!
In the end I worked at an RV place, building engines, trannies and rears full time for a race team that had IMCA modifieds, Late Models and Sprint cars. All for Free! That's right, worked there for 2 years for nothing, but since I had other income, it wasn't a big deal. But I could have worked during the day at the RV place and I did help the mechanics all the time when they needed and extra pair of hands. I learned alot about RV's and that there is no flat rate for A/C electrical and troubleshooting!!!!!