[Moses]

At your first suspicion that the lot was not buildable, you should have told the builder. Instead, you waited 7 weeks.

Now, you are looking at an opportunity to profit from your own mistake at the expense of a valued client. Is that about right?

If you value the builders business, sell the lot at market and forward the profit with a note to the builder. You will have enhanced your reputation and created invaluable goodwill.

Many years ago I found out that a senior partner recieved a "kickback" from a salesperson on a very expensive piece of equipment that I bought. That mistake cost him a great deal.