Machinist,
If your goal is to make money in originating keys for cars, the more work you do on your own and the less you use cash for code services, will boost your profit margin. I do not use cash for code services. I make my money on disassembly and origination from the lock cylinders. Start with Ford, Chrysler, and GM. Do the older cars first- impressioning skills will take you a long way on 20th century cars. Learn Gm steering column disassembly- including airbag procedures. A lot of locksmiths turn these jobs down, or pass them on to others, because they didn't take the time to learn proper procedure.
If you can afford it , you might try to pick up a set of Mike Hyde's Auto Smart Books.( I have no relationship with his company except that I am a customer.) They have a wealth of information and even if you could buy some used, they would help in steering you in the right method for each make and model for both domestic and foreign.
More to the point of your question- try to develop a relationship with your local dealerships, both foreign and domestic. Get to know the service writers and see if they will farm out some of the lock work to you. I do a lot of work for a Ford dealership simply because they do not cut keys by code for vehicles older than 10 years. People have their vehicles towed in without keys and they call me when they are older that 10 years. Also, the local dealerships (that I do work for) will supply me with codes by vin if possible without charge. It takes a while to build up that kind of relationship, but it has been well worth it. I try not to abuse the codes by vin.
Best of luck to you-auto work is most rewarding, and never boring!
Camelgd

Al