There is no easy way in and it's a difficult learning curve, you need to sign up for everything with a machining RFQ section and start quoting for jobs, you'll get it wrong several times and you will take a bath on the occasional job.
The best way to make money is to make things you can sell, the choice is yours whether you make things already being made and make them better/sell them cheaper or innovate and find niche markets which no commercial business can afford to exploit.
I began as a hobby machinist with a full time, well paid profession but I now design and manufacture my own products.