I am considering a career AND industry change, and I'm almost 40. Can you give me some general advice or pointers about career switching. I'm not entirely sure why I would think you might have a basis, just reaching out.

This is not an advice, but just a comment. I think many software engineers would KILL it if they worked for small mom and pop shops, or small practices. They could help turn many $500,000/year businesses into several times that revenue. Plus they would have WAY more autonomy then working at startups and tech companies, which in my opinion are just factories.

I agree with you, but there are a lot of catches when dealing with small businesses. They don't apply to every business, and my experience could be anecdotal. But there is an argument to be made that some of these businesses remain small for a good reason.

The first problem with many of these small businesses is they don't want to pay market rates for people with the skills and talent. If you do generate that much revenue, it's not guaranteed that you'll be brought up to a market rate.

You might not even get credit for achievements, where people view you as a commodity worker. You'll encounter owners or employees who know just enough to be dangerous, and therefore don't value the skills you bring to the table. Their son knows some HTML, how hard can it be? You can't build Facebook or automate all of their business processes in a weekend?

You'll be caught in situations where your time will be micromanaged to the point where you can't be productive. The farther away a business gets from software, the less experience management has with managing software projects and the people who work on them. It's difficult to get autonomy for a project that might take days and weeks for tangible results, when most people are used to being able to see the progress and results more immediately. They won't understand everything or anything you're doing and may doubt you actually know what you're talking about or understand their needs.

Your "maker's schedule" will be sliced and diced into useless microblocks of time. Because you know computers, you'll be tasked with keeping printers and desktops running. You will be the first person people disrupt throughout the day with any issue.

One of the issues with a late career/industry change that is often not discussed is the pain that comes with a (usually?) sharp downward adjustment in lifestyle due to lower wages, similar to Mizayuki's 80% salary cut.

Immediate family concerns and other obligations (e.g. parental care) at a later stage in life may necessitate a more gradual shift through successive job transitions, rather than a sudden career change.

Technically, an "experienced hire" should be attempting to shift into careers that allow for maximum skill transferal, but this isn't always possible, and it certainly isn't easy.