With this person's history, if you decide to board his dogs without payment up front, be prepared to keep his dogs for free. He didn't pay you last time and nothing happened to him. He probably thinks he can do it again.
We have had a few customers over the years that "forget" to pay their bill. When they call a few months later to order something else, we inform them of their previous bill and require them to come in, pay the old bill & pay for the new order. Then they are put on a "no charge" account. Cash or credit only. We've had a couple people get mad, but it's not right for us to foot the bill for someone who doesn't want to pay.
Good luck with what ever you decide. I hope he pays you this time.