I would increase your CapEx and Maintenance expenses (I use 10% each for older, lower valued properties), but I err on the conservative side. 

” (35 ILCS 200/15-175) The amount of exemption is the increase in the current year’s equalized assessed value (EAV), above the 1977 EAV, up to a maximum of $7,000 in Cook County and $6,000 in all other counties.Our scenario is my mother and step dad live in a SFR of ours and their rent is solely based on the total costs of the property (mortgage, insurance, and property taxes).

A laser tape measure speeds the process considerably.

I just increase my rents by $50 and say water is included, job done.

The price has increased quite a bit around 50%.  

BRRR is the strategy to grow our portfolio, ideally we can increase the number of cash flow streams and cash on hand to rinse and repeat.  

Is there potential to use it for AirBnB or some other short term arrangement to increase the income?

There WILL be other deals.Your knowledge/experience WILL increase with time.There's no reason why your Flipping101education NEEDS to be expensive.ie.

You make a considerable portion of your money when you buy, so you do not want to spend an unnecessary dime.

I shouldn't have said that it increases the cap by 1%, but just using that as an example to show how big of a difference it makes.This will double my # of units, so just want to make sure my numbers are tight.