Advice request -- buying an airplane

Hello all,

I have an opportunity to buy a 1978 C-172 that appears to be in better
than good condition for a better than good (for me) price. The logs are
current and an annual was completed in February -- I've talked to that
mechanic and he said the ship is in good shape.
I thinking about offering a $500 good faith deposit, refundable only if
I find something wrong in a pre-buy inspection and have cause to back out.
Does that sound fair? Should it be more or less?
I have a recommendation for a good mechanic who has never seen the
airplane but know nothing about avionics shops. The aircraft is nearby Wm.
J. Fox field in Lancaster. Any comments on the local folks there?
And to make things lively, I welcome any other suggestions about buying
my first airplane. Well, except from the PT Barnumphytes

Regards,

Casey Wilson

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