My gf once asked me if I had considered building models as a part-time job to make a little money, I answered:
The day that I build for money is the day that modeling stops becoming a hobby. I've build quite a few OOB's for friends and I didn't charge them a penny (except when I had to buy the kit for them). Why? Because I enjoy building. I get a bit of satisfaction after every brush stroke.
It all really depends what modeling does for you and what you get out of it. Is it the completed model sitting on the shelf? Not in my case, I have less then 10 on shelf and have made over 50 models over the years.
Or is it the pure satisfaction of success after you complete a part/ the kit? ← That's my case.
As for the fee, most of what I've seen are like near what
73superduty said. Roughly 100 us for a OOB.
My
Steve