
In my own breed where stud fee is the price of a puppy generally stud dog owners wait for the bitch to whelp before charging the stud fee.
If a puppy instead of fee is a definite then that is arranged, but if it's a wait and see maybe, then the fee would be payable and the stud dog owner would buy a pup like any other owner.
As for being maiden dog that makes no odds, all stud dogs usually are same price champion maiden etc, but in our breed most males get very little use in their lives, a dog used half a dozen times in as many years would be 'well used' and likely to be influential if pups go into gene pool.
To be honest as long as you make your terms clear, then you can do as you wish, if the bitch owner accepts the terms.
For example it is common on the continent to charge a fee for the mating, and fee per puppy.
The total would equate to the price of a puppy for an average size litter for the breed. So in my breed where just under 6 pups seems to be the average reared and pups being £700, then say £100 at time of mating (for the stud owners time and trouble) plus £100 per puppy would equal price of a puppy fee, with the bitch owner gaining if litter small, and stud owner getting more if litter large.