Your investment so far: You in all likelihood have at LEAST 20 hours in searching for, visiting and selecting the stallion. You travel costs, phone bill etc. have added into the $ amount you have invested. A realistic estimate would be $100.00 invested upon to committing to a stallion. Item Cost Research Costs $100.00 Stud Fee $500.00 Sub Total $600.00 Your mare has to be in heat to breed her to the stallion. You have one of two choices. Have your vet palpate the mare to assess the stage she is in heat, or estrus, the time at which a mare is receptive to a stallion, allowing for mating.