If you do build on a commission, you'll have to get used to building the way your buyer wants it built, not the way you want it built.

A buddy of mine in our club got a commission to build a piece of modern German armor, a Jagdpanzer of some kind.  It was a Dragon kit, and he had fun building it, but he got into a disagreement with the guy who commissioned it.  The real vehicle has a visible seam between the front glacis (sorry to sound technical--the sloped part of the upper hull) and the top plate of the vehicle.  The kit builds up as a faithful reproduction of that seam, and my friend built it, painted and finished the tank.  His buyer looked at it and demanded that he fix the seam.  My friend argued the point, and even showed him photos of the real thing, but it didn't matter, he wanted the seam filled.  My friend was so bothered by this that he almost chucked the model, but eventually, he came to terms with the fact that they guy wanted it that way.

You do also have to get used to the fact that you are making your hobby a business.  Even if you don't let it bother you, you'll have to meet other people's deadlines and expectations, and you'll have to be mindful of providing good customer service.  That's not always fun (as someone stuck in customer service, I can swear to that).

But if you can take on a commission and build and still have fun, you will profit monetarily as well as pursue your hobby.