What do apartments do for turnover cleans?

[Brendon Kelley]

My wife and I are starting a cleaning company for short-term rentals, but I also thought that turnover cleans for apartment complexes may be another good source of business since they would be similar in nature.

However, I am not sure if they hire that in house or contract it out? I'm sure smaller properties are unlikely to hire someone full time to do it, but at what size do they hire within (if they ever do). I am not familiar with apartment management. 

Any other info about the apartment cleaning situation is welcomed as well! TIA!