Some advice that I give both carpet and restoration companies in our area is this: go to all the first responders in your area (firemen, police, EMTs, etc), and your local military guys, and pass out business cards while you tell them you're looking for part-time help.
They are usually very energetic, highly motivated people with a strong work ethic.
They don't need babysitters or overseers once they've been shown how to do something.
They're used to the idea that if they don't do their job right, someone may literally die.
They tend to be mature, stable individuals who don't move around or make big life changes much.
Their schedules tend to be crazy (4 days on, 3 days off, etc) and if they're not busy with family they're looking for something to do with their down time.
Start them out as 1099s, and once they retire out of their full-time jobs (which they almost always do early), they are fully-trained and ready to sign on as an employee. A half-dozen of these folks in your roster is usually enough that someone will always be available when you need help. Of that half-dozen, one or two of them may well turn into full-time people.
When the housing market is down, you can also find GCs, plumbers, electricians, carpenters, and such with the same mindset.
Keep in mind that if you want quality, you pay for quality. Don't offer a Marine minimum wage to start. You might not like his response.