Having worked Operations at two different nuclear plants I'll second the recommendation for joining the traveling carnys that go plant to plant for maintenance shutdowns. Once you get through the initial radiation worker training and past the background checks you can pretty much pick and choose which outages at which plants you want to work.
And if you are a good worker and you keep out of trouble then you are going to be working 60-80 hours per week during the outage, but you get paid the overtime to go with it. The challenge is to not drink away your paychecks and to come up with a cheap way to live.
I knew a few guys who bought cheap houses near a couple of plants and rented out rooms during the outages too. They always had waiting lists for tenants and paid the mortgages with rooms that were empty 8 months out of the year.
There are a lot of jobs that don't get done often that you can get into as well. Someone has to install home elevators, stair lifts, hand rails, ramps, etc... things you only have done once. Security systems, door openers, gate openers, septic systems, heated driveways and sidewalks, skylights, radio antennas, etc... things that a regular contractor could do but doesn't do often or well enough to be competent or competitive.
Also consider bundling and vertical integration: one of the local powersports dealers up my my inlaws started selling docks. Then he started installing the docks. Then his crew that installed his docks started offering it as a service to install and remove docks for residents in the spring and fall. Then they started doing the same for boat lifts. Then his dock fabricator got a mobile truck and when they were moving docks and lifts around they could offer on site repairs and upgrades at the same time. Then they figured out that they could go much quicker working off a platform boat, one lake at a time. Then the platform boat became the perfect rig for teaching scuba off of in the summer. Then, since he had a great crew of strong guys, he started offering yard services in the summer and snow removal in the winter. Then they started offering up irrigation and cabin winterization.
The guy has customers who he bills monthly for essentially the annual service of doing the stuff around their cabins that they aren't able to keep up with themselves. The elderly, those who live too far away to be able to get there reliably on a given day, and to some extent the rich or lazy, they all just send him $x a month for piece of mind. I don't know if he even sells anything anymore, but he has 10 guys working full time year round and he pays them well enough to keep them.
You could inject yourself into that sort of thing anywhere: learn how to repair chipped windshields and get your local quick lube or car wash to let you set up out back on Saturdays, buy a pressure washer and partner with a lawn mowing company to offer gutter cleaning and deck staining to their customers, learn to clean chimneys and (after you swing by my place) tie your services to a roofer and/or fireplace installation company. There are lots of gaps around the edges of what even professionals do that you can fill.