Let's assume you accounted for all expenses and have a full $2,400 monthly cash flow.

In order to avoid questions from the tenants, I was upfront and told them that the current furnace is expensive to run because it is inadequately sized for the house (I didn't mention details about lack of a heat pump) and we made the decision to change it out for a gas one ASAP, which will go to their benefit, and all we need from them is to add gas service.

Make sure they know you plan to publicly point out to the local newspapers, Mayor's Office, and anyone who will be campaigning against them, just how stupid and lazy they are. 

@Tyler Garza With my CFO clients, I generally use 8% vacancy and 25%-35% operating expenses depending on if they are self-managing or using a PMC. 

The top three expenses in a flip are the rehab costs, lender fees, and sales commissions.

We put this in our offers to differentiate ourselves from other offers and we can write off this expense as a tax deduction.

Those are the biggest expense.  

The rent from the other units will allow your to purchase a more expensive property than you could on your own, which could help you build the value of your portfolio (and equity) faster. 

The East Rock area of New Haven (near Yale) is a huge outlier in terms of pricing, very expensive. 

My plan is to sell my primary home in New York and purchase a house to live in South Carolina.