Where I'm renting I've got 3 bikes, plus all the tools and other bike clutter. The bikes go in a shed. Spare tyres, wheels, panniers, etc., under the bed. When not being used toolboxes get a blanket thrown over them so they look like something vaguely furniture-ish. Any mechanics get done in the back yard in the summer - always nice with a cold brew - in the winter, a sheet has to go down in the room and it gets done there.
The shed isn't particularly secure, but then I don't think any of the bikes are *that* nickable. I used to D-lock them all together, but with the coming and going I just can't be bothered anymore.