You may feel you are the smartest kid on the block and that may even be true however, you cannot increase another person's risk and shed responsibility to another without their full awareness and acceptance and there are just too many holes in your permise which is why it is illegal. 

I bought a property last October in a small town in Northern MI. The property itself has 3 units on it. The owner/landlord that I bought the property from was renting them out way below market value with no security  ...

Of course, that will increase headache and responsibilities. 

Legally, I can only increase rents by 1.8% under new ownership unless there is a capital expenditure or significant increase in property taxes that justify it. 

If I can justify a rent increase, I will increase the rent and offer another one-year lease at the increased rent amount. 

I would loosen your equity to 70% so you can increase your mailing size.

How much of a rent increase? 

If not that will increase your All-in amount.What are you using for your Refinance loan amount?  

They are due for a rent increase that has not been completed by the previous owner.

But it may prevent you from borrowing more due to the increased debt to equity ratio.