I work for myself and I have a similar situation in terms of income. What I do is wait until two months later, look back see how much was left over and put a little bit of that aside for cigars. For example, in a couple days I'll go back and see what came in and went out in April and split what is left over between a college fund for the kid, my wife and me. I found that a 2 month lead time helps give a cushion for emergencies. That way my wife won't get mad when cigars show up at the door at an inopportune time. It also helps me because clients don't always pay on time.