Jenn~
I understand what you are asking for but I have no experience with this as I have never bred any of mine, male or female. I have read a lot on here and what I have read is what you have been told ....that the terms of the relationship and the "transaction" ...the contract....is between the two parties. Sometimes the stud owner charges a stud fee of anywhere from $150 to $1000 or $1500 I have heard for a champion stud.
Or, the stud owner can ask for a puppy from the litter instead or even pick of the litter.
You also have to address what happens if the mating doesn't "take" and the female does not get pregnant. Or, if there is only one in the litter or if (heaven forbid) the puppies do not survive. There are a lot of contingencies to foresee. It would be good if you could find a yorkie breeder in your area who would mentor you and she/he may have a standard type contract to cover this and then you could figure out the terms with the other owner and write your own using that one as a guide.
The mentor will help with a lot.
I would advise premating evaluations of both dogs by a reproductive specialty vet to determine their suitability for breeding and there are health tests that need to be done on both.
Good luck and PM me if you want a great website I found on breeding that walks you through the basics by a good vet.