@jerri I think this is 100% a good idea. I wish I'd started my own business much sooner than I did. Basically, the sooner you start this, the better.
Just an idea, you might look into towing a small trailer with your car while you're saving up for a proper vehicle.
I think adding a trailer hitch is less than $200. Harbor freight has trailers for I think about $1000.
It would make your drives a lot more comfortable. Plus, you can haul off the yard debris.
The following is not financial advice, and I am not a tax professional:
Unless you're getting paid cash for all your jobs (which is possible), you should look into forming a legal entity and talking about your tax write-offs and bookkeeping best practices with a professional tac preparer. Expect to pay about $80-$100 for an hour sit-down with them. I promise it's worth every penny. Also have them file your taxes. About $400, but again, you'll quickly realize it is very much worthwhile.
BTW- don't use a huge corporation like H&R block, you want a small business that is run by people who actually know what they're doing. Nothing against HR for the average joe, but most of their employees are just putting numbers into a computer, they don't really know a lot about filing taxes.
You can report your income as a hobby for a few years, but if I remember correctly, you need to be a business to write off your expenses and mileage. As a business, every piece of equipment you buy is tax deductible. Also, you get something like fifty cents a mile for business related travel.