There is no such thing as a minumum number of posts required to make deals or something. The thing is, a newbie account is created in a few minutes. If someone has the intention to scam someone, it's more likely to do this through an account that has been made within minutes than doing this with a Hero Member account (like mine), which takes probably more than a year and many hours of activity on this forum as well as posts made on this forum.
This results in people trusting 'newbie', 'Jr member', 'member' accounts etc less than 'Sr member' or 'Hero member' accounts for instance. Together with this, you have not made a succesfull deal yet (based on your trust rating; https://bitcointalk.org/index.php?action=trust;u=396213).
- -
More on topic, so I think escrow is needed if you want to make some sales and even then it might be hard to find buyers. However, everyone has to start from scatch on this forum. Goodluck!