Trav, While I'm not in the business, I have a half-brother that is and he's been in it for about 40 years. He's always busy in Central Illinois and has his own repair, installation, and contract service business.
He's always on call and seldom gets out of town unless he has a competitor to take emergency calls. Most of his free time is in the Spring and early Fall as AC problems always crop up in the hot weather, and Heating problems always crop up when the weather gets cold. Job security is pretty good in his area.
He started in a small 3 man shop (non-union) and when the owner retired 10 years later, he and the other guy bought and split the activities, customers, and leaned on each other for a few years.
Get a good Technical School for a background and keep up with the updates...