I don't think there's a reliable way to come up with an exact dollar amount that everyone can just plug into their situation and be 100% safe. 

I agree with Adam that there's not enough information here to say who is at fault.If you are spending all your income on maintenance after three years, then I would say you are being cheated by the PM or you bought a real dump.Personally, I would suck it up and find an expensive, but reliable, contractor to visit the property with me and make an assessment of what needs to be done to fix the property and stop the bleeding.

Do you have a network of reliable vendors?

I am currently full time employment in a reliable position.

Not aware of a reliable source for this info - and please don't think US Census Bureau is the answer.3) How do you account for "property condition"?

Are there any other types of real estate that might represent value sector, energy, healthcare, etc. 

If you're seeking a reliable income stream, consider checking out Cleveland.

Quick backstory: Tenants have been in place for almost a year and have always paid reliably, and on time.

**Property Management Recommendations:** Could anyone recommend reliable property management companies in the Nashville area?

Brookings OR - There is a specific zoning code that investors can reliably obtain a permit with the city.