The average cost of remodels (from what I hear) is between $90.00 and $120.00 per sq. foot. If you visit the National Association of Realtors, Realtor.org. page you will find 1190 returns on this very topic and will undoubtedly find just what you are looking for. Good Luck. Cindy Vedder.
I would expect to pay about 62,000 for a second floor Master Bathroom addition and a Guest Room on the first floor combined the total would be about $155,000. You have to check lot coverage first however before doing anything on the ground. When would you like that set of plans?