Nope, EVERYONE pays in advance. Period. If they don't like it they can leave. Seriously, if they REALLY value your care then what's the big deal? Ask them......."do you not trust me?". And then wait for the awkward silence.

Why does it always have to be US who accepts the burden of possibly not getting paid? I have knows A LOT of daycare providers in my time and honestly, only about 1% of those providers would knowingly screw over a parent. On the other hand I have read hundreds of accounts of parents not paying parents.

I just wouldn't take NO for an answer. This is YOUR business and you get to run it the way you want. And, personally, payment would be made in advance or I would let this family go.