I would be cautious based on no ratings or forum posts. The price is probably about all it would be worth in today's market. My red flags come from lack of information, no servo numbers, high end by who's standard? Incorrect name for the engine manufacture, mentioning high end retracts, if they are not skymaster who's are they? That is outside of the no history on RCU or ratings. All that aside he does list a phone number, it doesn't show up on a reverse lookup but it could be a cell number. The 20k number sounds very high but maybe he paid to have it built.
7k is probably about right for that jet turnkey in today's market sadly.
I would be cautious, for what it's worth, the sellers location is shown as NC, but 816 is a Missouri area code.


Edit: 411.com shows the number as a landline in Kansas City, Missouri