You can remove rust spots with a toothbrush and baking soda (ask me how I know...). 

Disposable old toothbrushes help in getting into the window tracks.2.

By midnight her phone and toothbrush are likely at full power and you can turn off the power to those outlets without interfering with the tenants' use of those devices. 

She could even have people have a toothbrush there and extra clothes because they stop over a couple times a week and get changed and showered before relaxing and watching Jeopardy together.

You can have cars, toothbrushes, underwear, roommates, at multiple places.

If/when the room vacated is filled with another paying tenant, then perhaps I would consider a pro-rated refund.I mean, really--a student got into an argument (non-physical) with a roomie and then their reaction is they took their toothbrush and blankie and went home? 

Stumbled on this service, which appears to be an interesting business model in itself and got me thinking about how this might work for convenience items such as toothbrushes, deodorants, or other items that are not necessarily stocked in the unit, but are often forgotten by guests coming to stay: https://www.thehost.co/Anyone using services like this?

Clean the grout with bleach and a toothbrush. 

Verify (with more pics) no toothbrush in the bathroom, no, or minimal food in fridge or cabinets, empty (of clothes) closets.

If there is no good food in the refer, no prescriptions in the med cabinet, no toothbrush, no shoes, nothing with obvious value, all signs point to abandoned property.