Building Diesels to Sell?

The undec Kato locomotive I bought to model CN 5008 came all the way from England.  I decided to buy some more detail parts from the same guy as he is going back to sea and is selling off some of his stuff.  When it came down to the payment, he made me an offer: I could have them for free (there's over $150 of new parts there) and build him a CN SD40-2W. non dynamic and with a winterization hatch.  He would supply the base model, pay for the needed parts and pay me in detail parts. So that was that, I agreed to it and I'm now building my first diesel for a profit.  Just today, he asked me if I could also build him an SD40U, to which I also agreed.   I never thought I would ever be building locomotives for someone else!