From working at an LBS that primarily services the college student bikes.

I'll tell you that rusting cables is likely the least of your concerns.
I only ever see it become a problem on ladies frames with full length curvy housings.
If it's a men's frame with straight cable runs and housings with breaks in them, water tends to drip out before rust forms.

no, your bigger concern is running out of air in the tires.
College students Do Not inflate their tires. Get the fattest tires possible so they'll be tolerant of running for months at a time at 30psi and falling.
Don't even bother trying to tell him that he needs to re-inflate weekly, it won't happen.

after that, the next most frequent problem is taco-ed wheels. Since bike traffic on college campuses mostly involves crashing into other bikes and inexperienced car drivers.

followed by brake pads wearing out (which may be a factor in the above crashing issues)
far too often I'll tell a student they need new pads only to get the response: "it's OK, I'll just use the other one till it breaks"
you'd think that hub brakes (drum brake, coaster, disk) might be a good solution to this; but it's not because that only increases the cost of replacing the wheel when it *does* get taco-ed.