Accounts payable is the part of a company that writes checks
  out. Accounts receivable is the part of a company that brings
  the money in. We're super-small (family company, I do the
  business side and I really keep it simple - not much fancier
  than having a checkbook). Anyway, what I mean is: there's no way
  to know if/when we'll get future customers. Lots of hope
  involved because the business we do (animal removal) is
  one-time-only for each customer usually, so we depend greatly on
  word-of-mouth and stuff, along with normal advertising crud.