Windows inside showers are drafty and they rot. You'd need to add changing out the window to the many expenses of moving the tub/shower. Do you USE a tub? A lot of people only have one for supposed 'resale to people with small children'. You can see where I'm going with this...lose the tub and make a shower in a portion of the same space. Least plumbing expense would be to put the shower next to the existing sink -- where the plumbing and drain already exist. This would leave space beyond the shower for at least a linen closet -- possibly for a second vanity and sink. (Check the elbow room and consider if two people would ever use this bathroom at the same time.)

I doubt they would stay for extended time in the US when they have severe health problems. It is not financially possible for a non US citizen to stay here and use the medical services by paying out of pocket. So for what the OP is asking - a small bath for non-stair climbing guests is definitely doable. I am sure your parents would not be complaining for the few months they are here when they have the chance to spend time with you and your family. You are being very shortsighted. Just because someone has some mobility issues doesn't mean they can't travel. My aunt used a walker for the last 18 months of her life, yet still managed to go anywhere she wanted by walking and using public transportation in NYC. A walker still requires more space to maneuver. Are you saying that the OP's parents won't be able to visit if they have a walker or a motorized scooter?

"Seniors don't want just a first floor bedroom suite, they want a one floor *house*. Why maintain and pay taxes on a house with stairs to a second floor that may get occasional use? There are some good reasons for having bed and bath on a first floor in a family home, but don't fool yourself that this transforms a family home into one good for Seniors." ^^ This. That being said, it doesn't sound like that is the issue with the OP, first house and all. Honestly, of the two options, I'm not sure which I would choose - I don't like either of them. I think the practical and best choice for resale would be laundry on the second floor with the bedroom/full bath on the first. Maybe you can put a sink in the garage if you envision needing a clean-up area? I toured a home one time that had the laundry in the garage right off the entrance to the house - I realized it wasn't a bad idea (the garage was heated) and for me was preferable to the basement, because, let's face it, as you get older schlepping down basement stairs to do laundry is just as bad as schlepping up to second floor stairs. All the area needed was some drywall to enclose it and it would have been a terrific mud room right off the house. (I wanted to bid on this particular house, but that is another story).

tangerinedoor: Disagree about curbless. They're notoriously difficult to build and often go wrong. They're also expensive to build. Not an endeavor to enter into "just in case". If you're concerned about disabilities, go with a MINIMAL curb, which is only 2" ... much shorter than the typical 4-6" curb. I have a "curbless" shower, for encroaching old age, as insurance against needing it! It actually has a slight curb, about an inch that can be flattened down if a wheelchair rolls over it. It is part of the shower pan - so I don't have any sort of fancy tiled shower floor, but here again, function over form - and it was less expensive than putting in a tiled shower floor, curbless or not. Mrs Pete: I"m always surprised so many people don't use master bathtubs; ours is used at least once a day. If you're waivering on the tub, go with a simple, standard-sized tub ... not a big jetted garden tub. That "covers you" for resale. I had only so much space allotted for my master bathroom, and as noted above, I want to age in place here. So - NO master tub, no matter how it will help "sell" my home when the time comes. NOTE, my region won't care about these issues as long as there is a tub somewhere - which for me is in the second bath, into which I put a standard tub/shower arrangement. If I feel the need to use the tub as a tub (I've done it twice in the past 3.5 years, essentially for soaking my feet), I can go there.. If anything, my kitchen, built for someone who loves to cook, is better able to sell this place.