Galvanized rusts from the inside and the pipes inside diameter decreases over time impacting the water flow. - The same issue with pipe material goes for water pipes inside the house.

As your family grows, the ability to pick up and move decreases, especially once the little one is in school. 

Evaluate historical and current vacancy rates, aiming for decreasing trends.Demographics: For younger populations, focus on proximity to parks and schools.

Great education which is a huge benefit when hiring a property manager.Cons - Return on time spent on managing properties decrease the more units added to the portfolio.

I would suggest checking out "expired" listings and "price decreased" listings...

It looks like you have a business loss which you can use to offset other forms of income.I don't think you sold it less than its worth, you likely tried to get as much as you can.Squatters decrease the value of a home, especially if you are selling the house with them in it.

If you pull permits and renovate, both your property taxes and insurance are very likely to increase, causing your cash flow situation to decrease.

On the weekday availability, I decrease the required minimum stay and the price.

I agree with many of the other members of BP in this post, Detroit is not an easy market, still many pockets in the city, poverty zones, local Detroiters codes that must be attended, but at the end of the day is a powerful and big American city that is coming back (see GPD/Capita increase, unemployment rate decrease -still high for U.S. 9% in comparison with a national average of 3.9%-, an improvement in the family household income) that can make SOME investment thesis work properly. 

I cant find a consistent source for a long period of time, but glancing at some different sources, the largest decrease I can find on a national level is a 1.7% drop from 2008 to 2009.