I have to slightly disagree with @William Carroll here regarding Ohio State's sophomore rule.
I do agree Ohio State will continually make efforts to keep students paying them for housing, and of course I agree there's greed involved. However, I don't feel the sophomore rule has affected landlords very much yet. This may change. In my experience working in property management with the largest manager of "student" properties in the area, occupancy remained essentially the same. With over 1,000 units under management, my company saw 2014 and 2015 occupancy of about 94-95% drop to about 93-94% in 2016. I'm not saying there won't be a further effect in the future, just my two cents on the matter!
If you can still achieve 93% occupancy or more AND you've got that added bonus that nearly all student's leases are cosigned by a more financially stable parent or guardian, I think student housing can still be a good niche. The main concern I've seen personally is high maintenance and CapEx.
I certainly agree that one should tread with caution, just wanted to offer a slightly different perspective on the matter.