most software i see today already has this feature built in. 

Similar but slightly different is in past downturns was there one primary cause or multiple causes. your research may shoe there is typically one cause of a crash but it is a different cause every time so it is not predictive. 

If so, what percentages are typical for these fees?

@Brandon Capelle My thought has always been to include those utilities in the rent as its typical for the area and good tenants would not allow you to charge full market rents plus water and trash. 

Second to trusting the person, another huge reason I do it is because first timers typically take far less out of the deal than an experienced person would. 

If not typical management expense is about 10%/month.  

You dont always have to take on 100% of the debt yourself and there are ways so that you dont have to put up any cash or at least very little instead of the typical 20-25% down payment.

I typically like to do at least 60-day notice and let them know I am trying to make the process smoother and don't want to put them in a pinch.

Typically rodents and pests live where there is a food source. 

I typically don't include a washer and dryer with my units, because they can be a service nightmare.