You should politely tell your parents and anyone else involved that this is your business and that you would like the opportunity to thrive or fail based on your own decisions. You are old enough to fly around the world and catch bullets for a living, therefore you are now a man regardless of whether or not your parents want to accept that.
You explain to all of them what the going rate for lawn care in your area is. Let them know that you don't mind giving friends and family a reasonable discount off the rate that YOU have determined.
If you still live in their house, just mow their grass. That's the cheapest rent you will find anywhere.
All that being said, Im 33 years old and my mother questions every financial decision I make. There is NOTHING I could do that she couldn't complain about. Needless to say I don't talk to her very much. You know your parents better than we do. If you know there not going to let you be a man and make your own decisions then maybe you should move out. Just remember that when you make your bed you have to sleep in it. So put some serious thought into whatever you do.