This is called reverse amortizing b/c rather than paying down your loan the loan increases over time. 

I have four property in the same city from D class to class b.

If you have enough funds in an IRA the alternative would be to establish a self-directed IRA, and have the IRA buy the property subject to existing financing (if your sister is willing to do that), you personally can't assume the mortgage b/c you are not allowed to provide a personal guarantee for IRA-owned property and have the IRA pay your sister for the equity.

We will be using a HELOC as down payment, however what can we expect when buying a distressed property in B/C neighborhoods in Akron for a BRRRR?

Property B Assume the loan with 4-5% interest rate, pay difference in equity $70k and pocket 300-400 in cash flow every month.

@Andres Safady now that you have a market, recommend you figure out the property Class you want to invest in.If you apply Class A assumptions to a Class B or C purchase, your expectations won’t be met and it may be a financial disaster.So, when investing in areas they don’t really know, investors should research the different property Class submarkets.

Option B is their price with the difference being seller financed. 

3.b) Be arrested and charged with trespassing?   

As an owner is it better to a) install mini splits or  b) make renter supply their own air conditioner.

In our experience, demand for Class B/C housing in still through the roof.