You can see that every year, the monthly cash flow decreases and gets much more affordable.

You aren't living for free, but your living expenses have been severely decreased.

list price is 125k it's been on the market for 155 days with continuous price decreases.

However, there are many cons which make me concerned:Philadelphia, PA: population growth rate is slowing down, high crime rates, low median household income, etc.Baltimore, MD: the population is decreasing fast, high crime rates, negative home appreciation the last 10 years, etc.I have a saving about 100K - 150K to invest.

You will likely have to decrease the rent (to accommodate the fact that you are now billing them for water) while increasing the odds that the water bill doesn't get paid by them, which means you would have to pay it (so now you are out of $ twice). 

Which means, taking out as much as allowed (now), even though it decreases immediate cash flow, the loan itself gives you the maximum cash back in your pocket - immediately!

In fact, most commercial lenders will be less likely to lend to you if you intend on occupying one of the units because it will require you to decrease the cash flow the building provides as an investment (5 units paying rent versus 6 units).  2)  Commercial loans are typically 25% down if it meets all of the criteria typically established by the lender. 

I am renting these properties, but I am concerned they will continue to decrease in value, because of little economic growth within this area.  

Downside: popularity may decrease as wages are comparatively low.  

If you can find a bank that will finance these properties, you will probably be paying higher transaction fees relative to loan amount which at these prices will SIGNIFIGANTLY decrease your COC returns.