Due diligence - what does it encompass?

[Cathy G.]

If you are a long distance investor, what strategies should I employ to ensure I have done due diligence before I fly out to see the property?

I can think of only a few things and I'm sure there are plenty of others.
Some maps tell me if a neighborhood is high crime- but what does "high crime" really mean? The entire area is D or F? or only some streets in that neighborhood.

A property manager might tell me if they are willing to work in the neighborhood. Can I ask if they have properties in the area? Can they show me photos of homes they manage?

I recently read about the person who almost bought a condemned home. Can I call the city and make sure the property is sellable?

What am I not thinking of? How does a prospective buyer do due diligence?