There are different ways in which you can charge for services. By the hour, by the project, by the page, or for something like event planning you could charge a certain percentage of the total event cost. Many VAs offer reduced rates for a monthly retainer option. With a monthly retainer your client commits to a certain number of hours per month at a predetermined rate. If you work less than the committed number of hours you are still paid the same. If you work over the committed number of hours then you would bill the client for the additional hours at that same rate or whatever is agreed upon,” says Diana and Kelly.