if u just plan on breeding him once...i say fix him. its not worth it to him or the female that u get. esp. for the female. if she is fixed before she goes into heat it decreases her chances of getting mammary cancer by 100% and after the first heat it decreases like 75-50% and drops more after that. for him he can develop marking in ur house (although i hear it is possible to break them of this habit, it is a lot of work), when he gets older his prostate will enlarge (gauranteed if not neutered) and this can lead to costipation, prastatic cancers etc, also having his testicles he has some chances of getting testicular cancer. so if u dont want to become a breeder i say neuter him. sure its fun to have little puppies and watch them develop...but i say the risks out weigh the benefits.