If someone wanted me to build them a plane, I would do it, they would need to pony up the materials and hardware, radio, servos, everything to get it flying and I would build it for them for a small fee for shop use, but that's just me, I wouldn't do it to make a living at.
If there was anything that I would do as a business it would be to actually laser cut the kits and sell them, but that is it, it takes too much time to build to be able to recoup time for money.