First of all, I am totally against irresponsible breeding. But I want to caution you about neutering too early, especially large breed. I dont know what kind of dog you have, so just want to make a suggestion and not try to push ideas to you, because vets don't tell us things such as this.
This is an article I would suggest you to read before neutering your dog.
http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf
15 weeks and you said he is going to get neutered in a month, so I assume he will be 5 mths old when he is going to get his surgery. This is early. When you neuter your dog, you take away the testosterone. Beside being a sex hormone, testosterone is very important to proper muscle and skeletal development. Go to any introductory animal physiology text book and read about it, you will know I am not making it up. So in the long run, especially larger breed, the body structure won't be proper and may have problem in long run.
I know this red rocket thing is sometimes "hard" to explain in front of children but it's just fact of life.