To OP. Yes offers must go through the official offer process. Know shipping cost beforehand. I have started to differentiate between East of Mississippi shipping and West of Mississippi shipping cost. Shipping across country invites problems with damage and delays. Offers on the East coast are more welcome.
Here's the biggie. Filter people out by how they communicate in writing. Do they write in complete sentences? Do they come across as an adult? Are they knowledgeable? They must be polite. I'm not greedy. If red flags are raised I am polite to that person, but really don't try to do business with them. This works. I buy and sell on Craigslist, Reverb, USAUDIOMART, and Audiogon. I have made friends and met cool people by following my own rules. If people can't communicate properly, I don't deal with them.