I’ve done software freelancing on the side when I was studying, before getting my first job. Things like websites for small businesses, software for small businesses, software products I’ve sold, network/IT infrastructure for small businesses. It was good money at that time.
However, It is not exactly the “be your own boss / work as much as you want” experience. On one hand, it was a lot of fun building all of the software, web sites, and stuff from scratch. On the other hand, (as I am aware now), software has a lifecycle, so shorty afterwards, you start to get bug reports, change requests, and most of the time you are fixing some problems, and you’re oncall all the time. Most of the money in software is made with boring stuff, such as maintenance. As an example: If you have an Android app, you’ll probably spend more time upgrading it for each new Android release and fixing bugs resulting from incompatibilities with devices, as you’ll spend on building the app itself.
In the end, you won’t have a boss, but the customer will end up being “your boss”.