Depreciation on the parts that you do not live in, mortgage interest and principle pay down will in increase your return.The key to it all is the low down payment.

I increased the rent to $850 in 2016 and just on August 1st, 2018 I got new tenants who are paying $875.

And naturally, contractors hate that.

Which research items you want to compile will tell you how/if a market will allow you to increase rents?

One of the best ways to improve a unit by increasing the number of units or bathrooms without increasing the slab size. 

Don't believe it includes sewer as the house used to be on septic tank and later added to the municipal sewer but I didn't notice any increase in the rates or mention of sewer on the bill, so I assume it's included in the property taxes.Why the big difference.

Since that data doesn't include 2016, 2017 or 2018 I'm looking into whether that vacancy rate trend has continued to increase.

If you are upgrading the kitchen appliances and are not able to increase rent or make the home more desirable, then it would be best to save the time and energy to focus on the next project. 

@Mat O'Grady Rentometer.com gave me an increase of 500$ per month for home similar homes in my area.

Otherwise, I just have a natural conversation with them and learn more about them.