This means you cannot raise the rents until the lease expires and then with proper timely notice. 

We are hoping to get our license this winter when our "day jobs" are slower.

If handled properly you can save much on taxes.

Best way is to get a realtor license.

I just find the prices a bit too high for rentals in Denton proper, but if you are patient and look around to communities like Ponder and Krum and Sanger, you might be able to find things that you'll be able to rent readily to people who work in Denton (county government, universities, very large medical complexes, etc.) but cannot afford to buy in Denton.

Must be lIcensed and bonded.

I fear that if I do not use it from the start I will not be able to use it anymore2) Are there good explanations and examples on how to do it properly?

He doesn't have to be licensed to buy your property It sounds like you are having seller's remorse and want to take the higher offer 

Check everything, have it all inspected by a licensed pro and go with him/her.

I got my real estate license in 2007 and my broker’s license in 2017.