Great idea... I've had great success offering custom orders and as CountryCents said, you'll create some wonder relationships with people and they will recommend you to others. You have probably already thought of this but just as a suggestion , with a product like your's where there is wording involved, I would have a sheet so you can print out what they want. You should write out their information and then have them sign off on it. That way you can read your own hand writing and there will be no question as to what printed. Also I would get a 50% deposit up front. Hope you don't mind the suggestions.
The very best to you and your venture.
Debi