Most people prefer the quality of a laser jet type of printer.
It will need to be able to handle legal size paper for some of the billing reports. Dot matrix printers are only needed if you will be using multi-part bills. You may re-caclulate the bills as many times as needed to get all of your corrections taken into account. Once they are correct, print them, mail them, and then process the month end for this set of bills. Processing the month end places the bill information into the Financial History file insuring that your records match the customer's records.