Second, just be straight up with them - you've been working a sedentary desk job plugged into a computer building software apps for all of your twenties, and now want to spend some time learning how to build real world things and doing some actual physical activity. You're not sure how long you plan to do it, but at least long enough to learn the basics of the craft of building houses and similar sized buildings, maybe six months or so. You're inexperienced at construction, but are smart, have an engineering and problem solving mentality and experience, and can learn fast.
With luck you'll find one willing to take you on and assign you a crew that will mentor you. They'll start you on easy tasks, teach basic things like professional hammering technique, how to use power tools safely, etc. All things you can get a jump on just by searching on Youtube.
That's the gist of it. There will probably be more than one firm willing to take someone smart and reliable and train them up, even if you're up front about not knowing how long you intend to do it.
PS - it also occurs to me another interesting kind of company to work for would be a local machining and manufacturing company, if any are in your area. There are all sorts of cool videos on Youtube about precision machining and manufacturing that might appeal to a programmer. Same process as above.
SkyMarshal's advice is sound. If you turn up, wearing steel cap books, an something resembling the appropriate clothing, and say something like "I can start now", I think you're in with a chance.
Here in Australia, particularly Tasmania, it's been so hard to find people willing to turn most days of the week I'd say you could get a job here tomorrow (okay, maybe not Saturday) for any number of construction companies.
My contact details are in my profile. I could potentially flick you some drawings for you to study so you'd be able to walk in and say "I can read a fabrication drawing and a marking-plan".
Another option is temp companies.
Get your forklift license or trucking license if you want more of a career.
1. Steel-toe boots
2. Safety glasses
3. Professional grade hammer *
4. Professional toolbelt
Show up with those four things and they'll take you seriously.
* practice with the hammer a bit first. There's actually an art to holding the hammer at its Point of Balance (PoB), flipping it with your wrist not your arm/elbow, and letting its weight and momentum do most of the work instead of your arm muscles. I can't find a video on this on YT atm, but will post one if I find it.