What are your individual expenses broken out?  

Older houses with some broken asbestos shingles.

now I have a broken outlet and I will go change it after my vacation.  

Tell them they may be evicted if the dog is not house broken and continues to damage the property.

In almost every case they would have broken a lease to accommodate their need to move.

One broken appliance and a special assessment could eat your whole profit for a year.

I would get in touch with Matt Landau (I sound like a broken record on BiggerPockets) but he's the guru.  

If, on the other hand, you spot broken windows, damage to the outside the house, or any more significant exterior damage, that usually means that the owner has applied a similar level of care to the inside of the house.

Do you have any stats broken up by zip code or area of town?

Home warranties on every house cost $450 up front but save your cap-ex long term by getting replacement of broken appliances & systems for the price of a basic service call.