One big issue is transportation. It is difficult to find a lot of shops in one small area, even in a city. If you live in the country it is even more difficult. Then you have to compare the cost of running a vehicle (not just gas) to the reimbursements to see if you are even coming out ahead. That depends a lot on the vehicle you are using and the price of gas. As a tax preparer you can figure that out. My wife has a Prius that I try to use but I have a van which is more than twice as expensive. My rough figure is a bit less than 25 cents per mile on the Prius. I have to plan a route for half a dozen shops in one day and use Mapquest to plan the route and total the mileage to see if I can make any money. If not, it is time to talk to the schedulers to see if they need the shop done badly enough to add something to cover the cost. Some will and some won't but it usually depends on how badly they need the shop done and how close it is to the end of the weekly/monthly/quarterly cycle.
I don't know what your situation is but if you depend on buses you will spend a lot of time for the money you make.
Also, if you are going to work for some Mystery Shop Companies you will want to get back in the habit of capitalization and punctuation for your reports.;-)

I just don't understand where the heck folks come up with 'just one way' as mileage, but it shows up often. . .

If you have no other work and you leave from home to go do one or more shops and you drive in a substantially 'best way' to get to the location(s) and substantially the 'best way' to return home then your trip mileage is the miles that is 'business mileage'.

If you have a shop at point A and you decide to go other non-shop places while you are out and the distance to point A is 7 miles but you put 40 miles on your vehicle before you get home, you should note that 14 miles were business (to point A and back) and 24 miles were personal. (If I went to point A and then stopped in a personal location that added less than 10% to the total trip, I wouldn't worry about the personal mile.)

If you have a job other than mystery shopping, getting to and from that job is considered 'commuting miles' and those miles are not deductible. You need to read the IRS guidelines to see how this applies to your situation. When I had an 'office' away from the house for a few months, if I did shops after work I figured I could justify the following. Normal commute to work 21.6 miles. Mileage on a day when I first went to the office and went to shops after work 36.9 miles. 'Commute mileage' 21.6, 'shop mileage' 15.3. Keeping good records of what you are doing and how you are doing it should satisfy IRS that you are making an honest attempt to play fair with IRS and your fellow taxpayers.

All fees and bonuses from all companies need to be included in your Schedule C, whether you received a 1099 or not. Reimbursements are not taxable and you can choose to include them in your Schedule C as income and deduct them out as a business expense or not include them in your Schedule C. I include them and deduct them back out so that my gross income line for the business matches all checks, deposits and Paypal payments sent.

There are legitimate equipment expenses you can use to reduce the bottom line of your business, such as a computer, printer, camera and supplies. Equipment generally has a 'useful life' of at least 3-7 years, but under Section 179 you can deduct the entire cost the year in which you purchase the item. Since this is your first year shopping, I suspect you are using equipment you own already. You can depreciate some of your existing equipment. To do this you will need to know the original date of purchase and price of purchase. Assuming the equipment is not already more than 3-5 years old you can have a business deduction for its use for that percentage of its current use that is business related. (i.e. Lets say I purchased a $750 computer on 1/1/2010 and used it 100% for personal use in 2010. On 1/1/2011 I started mystery shopping and used the computer 50% for business and 50% for personal. My 2011 deduction would be $38. Not a lot, but it helps . . . If I used it 100% for business my 2011 deduction would be $150. Video equipment generally has a 7 year IRS life expectancy, as do things like cell phones while computer software generally has a 3 year life expectancy.)