You shouldn't breed your male until at least two years because he needs to be tested for his eyes, hips and knees. Those tests cannot be performed prior to the 2 year mark. Also, you can charge whatever they would be selling the pup for(or really whatever you want) or you can ask for pick of the litter. When I stud my males, I typically ask $400/$500 or pick of the litter depending on female. Also, you should remember that just because your dog is a certain way does not mean that you will get a pup just like him. You should see the temperment of the female and also do not breed with a female less then 2 years and make sure she has been tested too.
The best thing to do is ask your mother in law if she wants a Pomeranian in general, then you can get a pup for her but if she wants one just like yours, I wouldn't breed just for that reason alone.
Hope I could be of some help!