Trucking career starts in May - Advice?

Hello all. Let me start by saying that I'm going to be wrapping up a good career in April, at age 51, and plan to begin a driving career, something I've dreamed of since childhood. I have an AZ licence and have considerable part-time experience driving tandem straight trucks - feed trucks and fuel tankers. Although I have my A licence as well, I have only logged about 18 hours behind the wheel of a tractor trailer and obtained my licence on my own - no drivers training. My question is this - is there any demand for middle aged, retired professionals like myself in the trucking industry, particularily in Ontario? I'd go with either straight trucks or semi if a company would train me up to their standards. City work is of little interest to me - OTR is what I'm looking for. Would the apprenticeship program be something for someone in my position? I'd appreciate any tips you may have for me as I get prepared for career # 2.

Hank