Business Expansion - Currently Garage Doors

Just looking to get a bit of advice. First off, I'm living in Toronto, Canada.
I currently own a garage door company installing and repairing residential garage doors & garage door openers. I pick up things pretty quickly and can usually do a job fairly simply after doing one or two installations in entirety myself and troubleshooting any problems I run into on my own. When it comes to working with my hands & problem solving issues that can arise in hands on work, I'm fairly good at it.
So now, I'm thinking of expanding my business into other areas of home improvement. The obvious next line to enter in my mind would be installing storm, patio & closet doors. If any agree or disagree, please share your input. I wonder how easy/hard this line of work is to learn?
The thing is, whatever I do end up offering through my company, I want to offer something that I can learn on my own, or can learn fairly quickly that has a high demand for business as the garage door industry does. I wouldn't mind taking any courses to learn things as well, however I couldn't go full time days since I'm running a business, so that's a major concern on when and where I could find courses sufficient to help me expand my knowledge and to get some experience hands on in order to incorporate new services offered into my current business.
If anyone from Toronto has any advice on where to take courses such as what I would need, I woudl really appreciate it!
Have a great night! A.M.

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