The place we were living when we got the Roadster had a NEMA 6-20 in the garage already for an air compressor the owner had when he lived there. So I was able to charge at 220V 16A which was fine for my short commute. The new place we moved into I asked the landlord if I could run a 6-30 (house only had a 100A panel and it's old - a 14-50 would have required a new panel) and he said it was fine. So my Dad and I ran 2 6-30's into the rafters for the Roadster and Model S. It should only cost a few hundred bucks to have a circuit run and I can't imagine a landlord not letting you improve their place - they could advertise that it's "EV-Ready" when you move out.
Thanks for the info. Ideally I can find a place that has outlets already in the garage that can deliver more than 15A. If not, I'll simply have to find someone willing to allow me to make the upgrade, which as you said shouldn't be terribly tough to find since it's a free upgrade to him (but I worry as soon as you mention messing around with the electrical system that they'll immediately be worried about you burning the place down). This also pretty much precludes me from renting an apartment, and would have to set my eyes on a house. Also, if I move around fairly often the hassle and cost of making this electrical upgrade a few times could get old. All things I have to consider!