Having been self-employed since 1990, I should write a book...........but I hate having to think and type at the same time.
Before you jump ship, you should have 1 of 2 things established.............a customer following or a dam good reputation. Going self-employed without 1 of either will be very difficult. Do you know any of the customers of the equipment you repair? Do they know who you are? You will need to separate yourself from others in the same line of work. If you are in a shop situation, you are usually just a piece of the shop.......and the shop gets the credit for machine repairs and the reputation.........not the guy that does the work.
Another thing is customer expectations. If you have a field truck and are charging....say $100.00 an hour.............expectations of your abilities will be high. If you were to go out on a job that a customer thinks may be a hydraulic problem and you find it is an engine problem.................what do you do, then? If you put yourself in the position of only being able to take care of hydraulic problems and nothing else, you are going to be very limited on the type of work you can do. It will be tough to survive in that scenario. You will need to be the "Johnny on the spot" that can take care of and troubleshoot whatever may come up. If you cant do that, your good competitors will eat you alive.
Collecting money has never been a big issue for me. I've got screwed a few times.........it happens..........you just have to learn from it and make adjustments as you go. Don't let the size of the customer and how much equipment they have, or the condition of their equipment be the guide for your prospective business customers. I would never expect the small company doing $1M a year to be near the same class of a company doing $50M a year in the way they take care of their equipment. Too many times throughout my career..........it's been that farmer with 2 tractors, that contractor with 7 pieces of equipment, my neighbor with a track hoe and a dump truck, that super small paving company that only does driveways, or that county that can find no one to do anything...............those are the ones that kept me alive when the economy went to **** and the big companies cut back on expenses.
Now the part that concerns me the most.........you stated you are in a position where you are thinking of a career change? Outside of the BS, do you love what you do repairing equipment? There will always be BS, even being self-employed........that will always be there. I would encourage you to stick this out, whatever it takes. Your time will come............you just need to have your ducks in a row before you make that leap.
A suggestion, and some here may not agree with it. When I was doing shop work, almost every piece of equipment I worked/repaired had a huge company sign on it.........or I saw the work order, so I knew who's it was. My boss NEVER contacted a customer after their machine left. I DID! A week after their machine left, I would call the company and ask how the machine was doing and if they needed anything else. This did 2 things...........I made sure they knew my name and that I was the one that took care of their issue. It also helped build a relationship with that customer when doing shop work would have never allowed this. The company I worked for considered it good customer relations...................hell, I even got paid a bonus from the owner of the company I worked for as he made an example out of my doing so. I never promoted myself to take business away from the company, so it was never an issue. What i DID do was put me on the map. ..........for the future.