As someone who does this full time I can give some basic advice for the OP:
1. Your budget is low. By that I don't mean that you can't live on $50 a day (or $1500 a month). I mean you can't live and run a business on $50 a day. If you want to "bring home" $50 a day you probably need to make $80-100 a day. For starters, not only are taxes not withheld any longer, but you will be responsible for 6.5% more than you have to pay when you are an employee. If your profit is $50 a day you will have to pay about $6.50 in FICA (the part that pays for Medicare and Social Security) and another $5 in Income Tax. So your $50 profit is now only $38.50. On top of that most people severely underestimate the cost of driving their car. You think oh I only put $10 of gas in my car for that $50 day. Well first of all that means your profit went from $38.50 to $28.50. More importantly you are not counting for the cost of your car. Yes, you already bought the car. But you will wear that car out and you will have to buy another car and if you have not accounted for that in your budgeting then you are screwed because your car died and you have no way of making money anymore. If you think you can get by with a $10,000 used car and you think it will last 100,000 more miles then at a minimum you need to account for $.10 per mile for car cost not even including gas or maintenance. And you absolutely need to keep that car maintained. Oil changes when recommended, good tires and brakes, etc. So let's say you drove 50 miles for that $50 day that you spent $10 in gas for you're now down to $23.50 in profit and you still haven't accounted for maintenance, parking, tolls, etc.
2. 20 MSCs is not enough. It's not even close to enough. If you want to do this full time you need to spend all of your free time for the first few months doing a few things. You need to sign up with every single MSC you come across. You need to constantly check MSC job boards. You need to keep good notes of when MSCs release shops. You need to keep good notes of what shops MSCs have. You need to spend some time checking the whole country to see what type of shops MSCs have.
3. You need to have a good record keeping system for shops you perform. It needs to keep up with the following information for each shop: fees, reimbursement, amount spent, total pay expected, date pay expected, and some way of identifying the shop (MSC, client, address, city, ect). You also need to keep up with the following information for your business: miles driven, tolls, parking, supplies and equipment purchased, hotel if spending the night away from home, meal allowances for taxes on overnight trips, bank fees, etc. This can be in any format you like. What works for me might not work for you. What works for both of us might not work for Shopper Z. Mine has evolved tremendously over the last 5 or 6 years.
4. You need to have a good record keeping system for shops assigned. I prefer to keep this separate from above. Many people don't. Find what works for you. What worked for me when I was only shopping locally was to have a spreadsheet with several tabs. Say Tab 1 was Escondido, and Tab 2 was El Cajon, and Tab 3 was Downtown. As I found shops I wanted to do or were profitable I would put them on the right tab. Ok there's a Bank A shop in El Cajon that pays $20 and a Fast Food that pays $10 and 3 gas stations that pays $10 and 2 retail shops at $15. I would put them all on that tab along with the fee and know that boom on Monday I can do these shops and make $90. That's an ok day, I'll go ahead and self assign. Then as I'm looking for other shops if I see something that fits on that day I can add it in. Or if I see something that can only be done on Tuesday I can go back and look to see if those can be moved to Tuesday. Keeping it separate made it less confusing and easier to look at for me. It might not for you. I also liked this format because then I could look and say hrm I only have half a day for La Mesa but I also have half a day for El Cajon and I can do those the same day.
There are reasons that a body stays in motion
At the moment only demons come to mind