Although I can understand why a potential buyer might want to see and try the item before they buy it, they are not allowed to do this as it is against Ebay rules.
The buyer has to agree to the sale and pay through Ebay before you can exchange contact details.
If they come to pick it up and change their mind about the purchase, you could then refund them.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
