And that's cool but to a very great degree these often boil down to an exchange of time for money (unless by services you mean SaaS which is really just a product business with a different revenue model). You can make a living but you're on a treadmill that you can't ever really afford to get off of, and it doesn't really scale other than by adding more people.
I mean it's OK, don't get me wrong - it's certainly better than a kick in the balls - and you can make a decent living from it. But I don't find it particularly appealing: I'd much rather be involved in creating products that you can sell over and over again. And, if what you've created is of value to others, why shouldn't you charge them a fee to use it?
(Btw, I'd also add paid support to your list but, again, I wouldn't want to build a business heavily based around providing support because support can really wear you down - or at least it can really wear me down. It's absolutely necessary, but not something I find at all enjoyable.)