Like stated above it depends on your skills and where you can reasonably take the dog in a year. Think about the birds you'll need, food, shavings, waste disposal, travel expenses etc. I think the price also depends on your resources you have for training like property and equipment.
I would think $300-$500 would be fair depending on your schedule and what you intend on including in the price. I would STRONGLY recommend a contract with a release of liability in it. Accidents happen and sometimes people are not very forgiving when it comes to their pets.