I agree with those above
I am a breeder and would NEVER impose on friend or customer to have them do such a life altering thing such as they are asking you.
That is above and beyond friendship as you have no idea the things you will be dealing with if you go thru with their suggestion -i have a feeling it won't end here.
What I am saying is this - if i haven't already made myself clear
GET YOUR BOY NEUTERED and forget the breeding thing