I will paint it for the buyer as well, and he is practically stealing it from me afterwards, but that's okay. I got the model for free myself, so I won't feel too bad about that, and it's a good first leap into selling models I modelled and painted. Would you be happy if I modelled this for you?
I am probably going to paint some Space Marine related stuff every now and then from now and and put it up for auction on eBay. Not that I consider myself an über-painter, but I bet people would be willing to pay money for stuff I paint. I will do it purely as a side hobby though.