How to handle seller issues

[Bill S.]

So I have a deal under contract. We just got title back and the property has a lien against it for about 10% of the value of the deal. So the seller, of course, has a number that they want to take away from the deal (negotiated the price based on that number). I'm not sure what he wants to do with the money but that number is important. Now that number is at least 10% lower. The seller is an unsophisticated chicken mcnugget. They do not have not fax or email. They will get the title report in the mail and probably won't read it or if they do they won't understand it. They won't likely figure it out until we are sitting at the closing table and the check is "too small". 

A little more background. The seller has to vacate the property prior to closing so at closing all his stuff would have been moved. The seller is not terribly motivated. He is selling because I was able to get him his number. I know the property was under contract a couple of times with wholesalers and they backed out because they couldn't move the deal and he wouldn't come down on his price.

So my question is how would you handle this? Tell him now and run the risk of him backing out because he forgot about the judgement or wait until the closing table assuming that he knows about the judgement and the figure was considered with his "number". Or something else??

Thanks.