"oh, that's common practice"

I was attempting to set up a pre-purchase inspection on a Tcraft at Ft.
Lauderdale.
The owner said he'd need a $500 non-refundable deposit before anyone
did the inspection. "they might nick the prop, or drop a sparkplug
or....". and he said "that's common practice".
Having looked at 5 Tcraft in the last three months, I knew that wasn't
common practice.
I'm thinking this is one deal I should walk away from, facing the
seller as I walk backwards.

Just as a sanity check though, have you heard of a seller requiring a
non-refundable deposit prior to an inspection? - Mike