Hi @Bobbee0
I let 3 rooms in my own home with only one bathroom, which I use as well!
I let to lodgers who stay 1-4 nights a week, whilst working away from home, and also to Airbnb guests when rooms have no lodgers, or the lodgers are back home.
When I have 3 lodgers in it works surprisingly well; they are folk who've been working long hours, with a long drive too on Day 1, and they stay in their rooms, chill & never see the others. Bathroom has never been an issue!
Hosting an Airbnb couple alongside one or two lodgers has always worked out. Tho' it requires guests who keep the bathroom clean!!
When there are no lodgers around, if 2 couples book on Airbnb I block the 3rd room, to avoid overcrowding. If 1 single & 1 couple are booked, I sometimes block the 3rd room and sometimes leave it available for Airbnb, depending on who is already booked.... If it includes an older couple, I think I might be pushing my luck to introduce a 4th & possibly 5th guest! If a young couple with a busy itinerary just using my place to crash, I might allow the 3rd room to be booked. Especially in high season when everywhere else is booked or expensive.
My listing descriptions make it clear that there might be lodgers or other Airbnb guests around. I think that is the key to guests NOT complaining! And my prices are cheap, mainly because of the shared bathroom.
I'm in the UK. I have a theory that British & European guests are more likely to find my arrangements acceptable than Americans/Australians who are used to bigger houses with more space & facilities....
One advantage of letting rooms to people who don't know each other, is that all my guests have been quiet and respectful of the others (and me.) Only once did it happen that 2 rooms were booked at the same time for a group of 4 (2 couples, Lithuanian students.) They were my noisiest guests ever! Gathered together in 1 room, drinking, chatting & laughing! I was mildly alarmed at where it might lead, but they just about kept the lid on it, & were charming and polite at breakfast the next day, followed by 2 lovely reviews!
A lady down the road does what you're proposing.... only lets second room to the guests in the first, and as a result tends to host families when letting both rooms. (Twin beds in 2nd room.)