Landscaper, If they are already customers? who cares. These guys are idiots. A customer is not going to leave you because of a written invoice. All they care about is the price. I have been in the business for 11 years now and trust me unless you have a vendors account with some huge franchise, don't worry about it. Quick books is just as unprofessional. When you get going Get Real Green invoices. Lawn Assistant is the best program out there. Make sure your estimates ,flyers, and business cards look the best. That's what is important. http://www.perfco.net/ has some great estimates and flyers for the business. Don't let these little guys tell you anything.