Let's see... I've been riding bikes for over 40 years, on a regularly basis, and I've never had more than one bike at a time unless I've been trying to sell an extra one. Seems to me that there's plenty of money that can be spent on one good bike, plus the shoes, the helmet, the clothing (for all the different weather conditions too), the tires, the maintenance, a floor pump, a frame pump. I don't really know why so many have to have a stable of bikes (unless you have a specific need for a mountain bike, a good road bike should suffice).
But, anyway, I do live in a downtown urban area, in an apartment, and we already have 3 bikes in it: mine, wife's and daughter's. It's a small apartment, so one bike lives on the balcony except in winter, one is in a hallway, and the other moves around from room to room depending on where I feel it's safest at any given time. That's mine, and the small apartment gives me an excuse to keep it in or near the living room most of the time just like back in my bachelor days.