Deposits on parts

I too sell parts on this site, and the other alphabet soup, lettered, sites, here on the internet.
So i will give you my to cents worth, in regards to your question.
I don't find anything wrong with you requesting a deposit on payment for parts that you would be selling, and having a non refundable disclosure.
That way if a person is really a serious buyer for the parts, he shouldn't have any objections about paying a deposit.
At least with a deposit, more than likely they will follow through in purchasing the parts.
But i think in the real world of things, people buy the part(s) and pay for them in full, from the get go.
What irritates me is when people tell you they gotta have the part, can't live without the part, really need the part, and both agree on the part cost, shipping, give them your Pay Pal address and then they never follow through in paying you.
Why do people do that from the start, if they aren't going to be following through.

What i now do with any local Craigslist sales, i tell interested parties that i want a deposit on whatever you want to buy from me, put payment into my Pay Pal account, and you pay me the cash balance when you come to pick it up.
That has been weeding out all the shoppers, tire kickers, look-e-loo's, low ballers, from the start.
Seems to be working out for me, the way i now do business on Craigslist.