As someone who left full time employment at age 24 to open my own lawn & garden service I heartily endorse self-employment.
I further recommend service oriented businesses because if you're willing to learn how to do things others don't want to (or cannot) do for themselves, you'll always be able to find work.
I do believe that such a move only be done in a population center of at least 250,000. That large a population is needed to help ensure that you'll always find work if you're sufficiently enterprising, honest and dependable.
After just a couple years learning how to do your service job in dependable fashion, you'll be able to gradually increase your per hour charge. Additionally, if you have decent organizational and management skills, you'll be able to recruit people to help you do the jobs and you can further increase your income through the difference in what you pay them and what you charge for their man-hours.
In short, I'll submit that within four years you can become pretty much an expert on at least one, and likely several areas of personal service and if you demonstrate sufficient enterprise and dependability, you'll enjoy an income equal or superior to most any other profession for which you might invest a similar four years in via obtaining a university degree.
Best of all, you'll be the boss and as you move into your fifth year and beyond, you will have the option of expanding your operation wider if so desired.
Finally, if you're not fully confident to start a service oriented business on your own, I suggest finding someone else who is doing the type of work and offer to go to work for them in an apprentice fashion. This may mean working for a lesser wage ($10-15 an hour range), but if they have a decent operation, the education you'll receive in how to do the job(s), deal with the customers and how to obtain new business will more than compensate for the lower wage.