Be sure you have a perfectly clean and sanitary place to do it, and an appropriate cooler. (The just ok scenario many of us may get by with for a single deer or two a year is a far cry from what we would consider acceptable from someone we are paying to do it). Do you have the means to get rid of the byproducts..legally?
Are you prepared for all the dissatisfied customers you will have? (not questioning your work or honesty, just fact of life in any business).