I’m in Canada and the townhome we just bought used “master bedroom” and ”second bedroom”. The bathroom is actually “master bathroom” too, though en-suite is more popular. I think “principal bedroom” works well, especially if describing short term rentals (where multiple couples might share a rental), rentals by you adults (again where roommates might be sharing), or multi- generational homes. You still want to confirm which room is the largest, but there isn’t a need to explain who then “master” of the home is. Random point- when I’ve booked Airline tickets for my son, he always gets the prefix “master” vs “Mr” on his tickets/booking. Hubby and I always get a good laugh, as there are definitely days where it feels like he runs things in our home! Maybe he should get the new master bedroom haha.

There is no way to give an meaningful estimate, mother than to find out what the local average for price per square foot is for the work you want done---add on/remodel versus new construction. If there is no plumbing, the cost should be lower. But, costs/fees for surveying, soil compaction(for foundation) and permits/etc. have to be considered. Sounds as if the plan would increase the value of the house to some extent. My personal belief is if a person wishes to spend decades in a home, has the money to spend without putting their finances upside down, and simply wants the home to be theirs and comfortable, who cares about resale value

Some people really want/need an en-suite bathroom. Some people would like one, but can live without it if everything else--location, price, other amenities--fits their needs. Some people really don't care either way. And some people really don't want one. So if you buy this condo, you have eliminated the "really want/need" folks from your potential buyers and renters. But you still have a fairly large pool of potential renters and buyers to draw from. If you add the shower to the downstairs bathroom, I think you will make the condo attractive to non-related renters--three grad students, say. Do other units in the building have en-suite bathrooms? If so, then not having one could be a liability. But if there are other units without one, and the building itself is a desirable place to live, then you should be fine. You might have to lower your asking price to draw people in, but that would be the main drawback that I can see.

Thank you to everyone for their ideas and comments. We are currently working with a designer with engineering experience. There will be another ensuite room downstairs which could function as a 2nd master for resale concerns. @new-beginning - You got the idea for why I don't want all three kids upstairs - thank you! When my sons are in HS, my daughter (and her friends) will be 4-11. My boys are VERY respectful, but I think we all know how *some* boys talk and what they talk about in HS. My boys WILL have friends over and if they're all upstairs having a sleepover or just hanging out, watching a movie or whatever, I really don't want my daughter (and her friends) hearing conversations, etc. that are not age-appropriate for her/them. @Beth H and bossyvossy - I am most definitely NOT letting my kids decide anything about this house! They actually don't want to leave our current house at all :) They won't have any say on anything in their room or the house set up or anything! This is all for how we believe the flow will work best for our family. @chocolatesnap - You may be right, but right now, we cherish our time after the kids go to sleep. That's the only time we have to watch a movie together or enjoy a glass of wine or whatever. I am sure that we would still be able to isolate ourselves on the same floor with the kids though. Thanks again, everyone. I think while the upstairs retreat still sounds amazing to me...the costs involved with adding a second floor probably outweigh the benefits.