Raye -
1. First and foremost, understand that if you are going to make money doing this, you are operating as an independent contractor in charge of your own business. If you are going to succeed, you will have to put in some work. The more time you put in up front learning and signing up with companies, the more quickly you will be able to increase your profits.
2. You want to read the "New Shoppers" area on this forum. It will provide a full overview and a ton of information about mystery shopping.
3. There is a huge list of companies linked below. They are all legitimate. They may or may not currently have work near you, but that could change as clients change MSC's all the time. Plus, there is only one way to find out. I suggest starting with the "15 Most Discussed" companies as they are all larger and are almost certain to have work near you.
4. Though we are reasonably friendly here, keep in mind that we are actually competitors. If you become a successful shopper in Oklahoma, another shopper will lose work and/or have to work for lower fees. This business is pure capitalism and driven by supply-and-demand. So, there are limits to how much "help" most folks are willing to give. Respect those limits. For example, the list of video shopping companies is more than I would have shared.
5. My gas stations.... Here's the deal: You will not likely get deals like that tomorrow. I began working with this particular MSC about two years ago and have completed quite a few shops for them. I have NEVER canceled an assignment and have never had one rejected by them. I have built a reputation with them for being willing to drive out to the boonies to do a shop they are desperate to fill - and they know once it is assigned to me, it will get done. They call me when they are desperate to get something filled and we strike a deal. This is not uncommon for established shoppers..... My profit: Not included in the $850 was $60 in gas reimbursements. I have a car that gets great gas mileage and I figure I burned about $50 in gas over the 600 miles I drove. I spent about $30 more than I would have otherwise in caffeinated beverages and food. (I had three four-shot lattes today...) So, my profit was about $830 minus wear-and-tear on my car.
I hope this helps.
Hard work builds character and homework is good for your soul.