Safest way to buy a cel? (first time cel buyer)

Hi there, I am new to buying cel's and I want to buy a cel from a particular person. They said they didn't want the deal over eBay because they wanted to keep it as a private sale. Would getting the person to put the cel up on the rubberslug market be safe? I am paying with Paypal as well. Thank you, any feedback is appreciated. :)

PS. My other thread wont load for some reason. So if someone could delete it, thanks.