I did a mailer post card a few years back. I can't recall the specific number but it was at least 15000 households. I got 2 calls and was able to meet with one of the two for an estimate for weed control who wanted his yard sprayed one time. His yard was full of weeds.
Advertisement professionals will say that you can't expect immediate results, that is all a matter of keeping your name in front of the perspective buyers through repeated attempts. Personally I think mailings are huge waste of money. The people who read the advertisements that come in the mail aren't the people who are going to use my service.