Attempting to make mystery shopping full time depends a whole lot on where you live. At this time with the companies we deal with, shopping is done on an Independent Contractor basis job by job by job by job.
Here are some things to consider:
As an idependent contractor you have no traditional benefits at all--no health insurance, worker's comp, unemployment, sick days, vacation days, retirement plan, etc. These you must arrange for yourself if you are going to have them (and for the most part your flexibility with your own schedule can allow vacation time or time not shopping to meet various personal needs). If you earn net more than $400 per year you will need to pay Self Employment tax. In a regular job environment, this is the FICA pulled out of your paycheck where you pay about half and your employer pays about half. As an independent contractor there is no withholding and you pay both halves of FICA.
Most jobs available as you are getting started are going to pay between $5 and $15, with the bulk of them in the $7-$10 range. As you build your reputation with various companies you will more frequently be awarded shops requested that pay somewhat better. How many shops you will need to get to make this work depends on how much you need to get out of shopping.
If you live in an area where there are many chain stores and franchises you will see more shops than if you live in an area where there are limited stores. You still may have many shoppers in your area, so shops may be scarce.
Most of the folks who are doing this full time put a lot of miles on their vehicles doing long routes. Is your vehicle up to this and your home situation such that that is feasible?
You cannot reasonably go into this with $0 available to you. The vast majority of shops require that you make at least a small purchase ($5 or less) to obtain a receipt. That receipt is essential because it is your proof that you were at the right place at the right time. Time frame to be reimbursed and paid your fee varies from a very few companies that pay in a week or two to companies with a 3 month pay cycle. Once you have done this for several months, the cash flow gets better as there will be a stream of payments coming in via check, direct deposit and PayPal, but getting that stream going requires some cash up front and patience.
As far as "process in place", as a shopper, everything is up to you. You need to register with companies, you need to check their job boards for work, you need to keep track of what you have requested and what is assigned to you, you need to do any certifications for the specifc jobs, read the instructions carefully, do the job, collect your proofs of visit, enter your reports in a timely fashion, respond to editor questions and patiently await payment, keeping records of payments received both to know you got correctly paid and for doing your taxes later.