However the challenges of owning or managing those properties are numerous and difficult.Between 2009 and 2012 you could buy houses in good areas in Arizona, Nevada and Florida for 100 times monthly rent, with a little negotiation.

There are numerous post about it.

@Michael Baum I can show numerous examples.

You do not have the ability to add classes or subcategories which is a major drawback and makes things very difficult once you get numerous properties.

When discussing parts of a project with my contractor I'd go through every element of the project "so how much will the plumbing cost? 

Tenant has received numerous warnings on paying late, but at some point, landlord do not want to be  alarming and cause tenant to leave.

Some municipalities state a specific number of dogs, some just say a "reasonable" amount -- meaning if they are able to care for them (e.g. they are not starving or critically I'll, have shelter from the elements, etc).

Depends on what you value more, the numeric return or the ability to see the property in person. 

Make sure the mobile home's electrical system can handle the amount of power these space heaters require, and stay away from those that blow out hot air that might catch draperies or furniture on fire, and instead opt for the "radiator" style ones that don't have a hot element or fan but instead offer radiant heat that won't catch things on fire.

All of those questions have been asked and answered numerous times throughout this site.Get your education first, starting here and add local real estate meet ups to meet others doing what you want to do.