I just changed professions after 20 years of being a forester. Tomorrow, I will landscape all day. If it rains me out, I will do maintenance work for rental owners. Changing faucets, fixing water leaks, doors, etc..... In another couple of weeks, I'll be mowing. I'll then mow about 30 yards in a 14 day period. I'll build decks, remodel homes, roof, pour concrete, lay block, etc... for the remainder of the 5 working days. I work on Saturdays when the working weather is good. On Sundays to if need be. Come fall and winter, I will pick up the construction work full time. And, push snow around that.
I made this move to be able to hunt more. It has been slow getting started but, things are cooking now. This country is booming. So, pick a side job that requires labor. People don't like labor. I grew up driving nails. So the transition back was easy. However, I started in the lawn care and landscaping stuff by going to work for a buddy that does maintenance, landscaping, and mowing. I started advertising and picking up work for the evenings and weekends. I'm now getting pretty busy on the side. Praise the Lord.
So, pick a field, start you a business with the state, advertise, and get to it. Depending on your hours, if you landscaped and mowed alone, you could easily make $1000 a week extra if you are willing to work till dark and on weekends. Its competitive and will take some time. But, you will have the opportunity to grow it as needed. This applies to whatever that field is you chose. As long as its labor based. And, start a licensed business. Insurance is cheap too. You'll be AMAZED at how much more work being a licensed business and having insurance will get you.
Good luck brother. The last piece of advice I will give you is to give the Lord his share first. Before you take a dime, give him his due. He'll give you the resources, the strength, and the leads to develop this to whatever degree you want it to be. Go get it man. It is wide open. God Bless