Also, the ones that don't pay upfront and then you have to ask at the end for payment,
Do NOT let this happen.
Even if it happened before change and take the money first ALWAYS. And then go put it somewhere that he doesn't see and somewhere that is separate from the rest of your money.
Because eventually, the ones who haven't paid up front will turn out to have no means to pay you at the end.
And secondly, if you ever get robbed, you don't want the guy to take all your money. If you keep it in separate places he'll only get some of it.
ALL the decent punters will expect to pay up front and will not be offended when you ask for it.