agreed. this isn't a "side project", this is a "side business".

And this is why I would make to sure to log all the time that I spend on that side job, so that I can make some estimate about what my hourly rate would be with the earnings I make.

This might then allow a better decision on whether it is a worthwhile endeavor or not.

At the very least you might be able to write off some of that cost and get some money back/owe less money to Uncle Sam