If you search the internet, you will find some samples of breeding contracts.
Some things you will want to cover:
- mare health requirements ... e.g. proof of vaccination, coggins, clean culture, etc.
- when is payment expected and how much
- breeding season dates (end and start of your breeding season)
- how will the LFG, if any, be handled
- cost of mare care and what mare care includes/does not include
- liability statement incase the mare gets hurt or sick while under your care
- when you will provide the breeding certificate and stallion report (if any)
- if you expect the foal to carry a particular name, e.g. part of your stallion's name, that needs to be in the contract
I personally would rarely pay much for a breeding unless the stallion has already proven himself by producing high-quality foals, no matter what his own show record is.