I read that your seller is bringing the 150 you are buying to your FBO for the pre-purchase inspection. I am glad. I looked at a 1977 150M this past Sunday at Milwaukee. My FBO is at a small airport only 30 miles away. Still, the two A&P's selling this 150 refused to bring the airplane over to my A&P for the pre-purchase inspection - even when I offered to pay for gas and oil, they still refused because "The pilot will have to sit for 8-10 hours without being compensated!" They wanted him to come to them, but I can only imagine what difficulties they would give my A&P. Needless to say, I walked away from this one. If you want the complete history, look at the posts under the subject (Turned down the 150M, seller got hostile". I think your seller is reasonable and fair to fly the airplane 200 hours to your FBO and I wish I could find such a seller. Good luck on this one, sounds like your on the way to a successful purchase.
Steve