The rental house we stayed in had a small elevator built in. It was just large enough for Skip in her wheelchair and one other person.
It worked by opening the exterior door in the manner you'd open any regular door to a room (ironically, you can see it is opened with a knob rather than a handle). Then, the gate slides to the right, though it required a fair amount of oomph to push it. Once inside, the exterior door and gate must be closed before the elevator will move.
As you might imagine, it wasn't possible for Skip to operate this on her own. Even if the doorknob weren't an impediment, she'd have to back on in order to close the door and gate. The strength required for the gate manipulation would have been more than she could manage. But, with all that said, the elevator was a great boon. The house was set up so that the bedrooms and kitchen/dining/living room were all on the top floor (some of our friends theorized this was to take advantage of the superior view on the second floor). Clearly, none of this would have been accessible without this elevator.
Our dogs, Ruby and Sally, were a bit freaked out when they rode the elevator the first few times (they don't know how to climb more than a few steps at a time). Within a day, they were well acclimated, as were the 2 pugs that were with us. The labs took the stairs.