Ellen G. Friedman, Keller Williams Realty, email@example.com or 617-448-1542 http://www.ellenfriedman.biz
If you have the funds and the right contractors to help you get the job done and done correctly, I say go for it.
As a realtor I hear clients complain that they have to go downstairs in the middle of the night to use the bathroom.
I think it would help you sell faster, and you should see a return on that investment. Or, you could give an incentive to the buyer, say $3,000 - $5,000 for a bathroom installation. Also, make it a full bath not a half bath. Good Luck!
Lucido Real Estate