Please check for errors and correct them. Thanks!!!
I received your proposal concerning our collaboration on a play. Your basic plan sound fascinating.
I have a cabin on the north shore of Lake Michigan, and if we decide to write the play together I would be happy to offer you my hospitality, during the time we are collaborating on the play. The cabin would be a quiet place to work. We could get away from the noise of the city and really concentrate on the manuscript.
Are you free on Tuesday, August 9 at noon? We can have lunch and further discuss the possibility of collaborating on the play.
Plan is singular so "sounds" is what is required here. No comma after hospitality but after together.
Sra