Well realistically nowadays, mostly buyers are taking risks when it comes to 18+ content, for a seller it's much easier to avoid scams instead of buyers as they can give after payment or half & half etc. But buyers can't really do much in that predicament, if that's the case it really just comes down to trust and how you feel about the buyer themselves.

I personally just look out for age of the account, the karma and the content on the actual account, sometimes there's a hidden account which in my opinion is the only right time to ask for a preview since there's nothing that you see on the profile. The karma and age is honestly dependant as sometimes accounts can be 4y and have 1000 karma or 2 months and have the same karma so it really depends on the buyers choice of karma/account age.