Scam, Scam, Scam. If they won't call and talk to you, are out of the USA or have a health problem why they can't come to you, they are just trying to steal your hard earned money. They will send you a bogus bank check for more money than you are asking and want you to cash it and forward money to their shipping broker. You will be out that money if you do that.
Don't be so desperate to sell your stuff to be taken.
I have bought and sold over 140 items on this site, but every one was verified by phone and with pictures of the item and the person with a verifiable date. I still got taken once because I let greed get in the way of my judgment.