The risk will be the buyer coming after you too, if they end up losing money with a forced purchase to the TM holder.
But if it's a straight four letters, rather than nnn-m or n-mmm, then it is unlikely to be a problem as a domain name - it only would be as a site that plays on the similarity. So your 'sales pitch' could catch you out if you appear to encouraging such use.
If the domain's only 'value' is to someone who wants to misuse it, then your sale at an inflated price (compared to fhjbgfgnx.com, for example - a fictitious site, I hope), points the finger straight at you.
I suspect you are in a no-win situation. A classic double whammy.