Mystery shopping will not cover financial needs like a regular job. Let me encourage you to at least look for a full time or substantially full time job if it is humanly possible. It may not be in your precise field, but at least it offers the financial security of a paycheck and often benefits such as health insurance, sick days and such. Then if you additionally you want to pick up some extra work, mystery shopping may make sense. I have been doing this quite some time and my best month every was last year when fees + reimbursements exceeded $2000, but the fees were less than half of that. My highest fees month was also last year with fees of a bit over $1000.
The economy is affecting both the number of jobs available and the numbers of shoppers attempting to make ends meet by grabbing anything and everything. My best fee month in 2008 is about two thirds of my best fee month last year. And in general the fees being paid are DOWN, the number of shops being done is DOWN and the number of shoppers competing for jobs is UP.
That discouragement being said, you need to be signed up with the companies that have clients in your area. You can find out who many of these companies are by looking at Jobslinger.com. This is a free sign up that lets you see what companies and types of jobs have been posted in your area over the past few months by a number of different companies. While those jobs are likely to be gone, the company is likely to shop the client again, so sign up with the company and directly check their job boards on their websites frequently. Generally the companies will not contact you directly for jobs, you need to put in requests for them or self-assign them to yourself when possible.