@Jered Sturm@Marc C.I work in commercial solar for my day job, so this is something I have encountered with property owners asking this same question. In general, solar for multi-family works in cases where the common area bills are higher than $300 or it is mater metered. One big roof is more cost effective than putting panels on multiple smaller roofs (depending on the project, that can be a deal killer).
You're meter will spin backwards when you are making more power than using and get credits on your bill to offset times when the sun isn't out, but you can't over produce and get money.
There is a 30% tax credit (not deduction, but dollar for dollar credit) and accelerated depreciation (6 years) which depending on your utility expenses make the payback anywhere from 4 (CA, HI) to 9 years, so more than likely it should be a property you plan on holding for a while.
If you don't have the tax appetite, you can get an operating lease where the financing company will take the tax credit and you'll have lower payments. I would steer clear of SolarCity and their PPA's. I agree that their roof shingles probably won't make sense for a few years and are mostly for high-end customers.
Hope this helps.