Little late to the party, but tint and PPF are our bread and butter.
We've been using Llumar for over a decade and used to use 3M. I would say 3M and Llumar are on the same level and I've heard good things about SunTek, but haven't used it much.
GAC05 has a lot of good points:
It takes time to learn, expect to burn through several rolls before you're anywhere near good enough to install on a customers car.
Shop must be clean and don't expect to use swamp coolers or fans because they blow too much dust around and you'll get a dirty tint job.
Quality is key. Most people don't notice or are forgiving of a few specs of dust here and there, but there are some customers that will not accept a SINGLE spec of dust in any window. Just know there will be people that demand it's redone until it's up to their standards.
I don't agree with pricing going lower over the last 10-15 years; we've actually raised our prices a bit as the price of film has increased. There will always be someone doing it out of their garage for way cheaper than you can install it at an actual shop because of virtually no overhead; it's no different than the print industry.
I wouldn't worry too much about having insurance that covers glass breakage. In my 13 years I've never seen a back or side window break because of tint installation. I've heard rumors of it happening, but out of the thousands of cars we've done over the years it's never been an issue. A few cracked windshields from people not knowing how to remove the rear view mirror, but literally just a few.
Llumar will set you up with a free plotter (I think they're using Graphtech FC8600 these days) and a PC along with access to their pattern database if you agree to purchase a minimum amount a year.
If you are serious about window tint, you might as well look in to doing paint protection film as well.
Edit: Oh, and NEVER use a carbon steel blade on glass, it will etch it. Stainless steel ONLY, and even then be light-handed.
