It’s probably easier to just raise the rents to cover your utility costs or look into electric heat pumps.

And, just for fun, I also included potential gains in the stock market (opportunity cost if he invests in stock market v. rental property) for the 5 year period at an industry standard 7% gains and also an optimistic 10% gains in investments.

Utilize your strength and go for it.

I'd just ask what condition the property is - if it's not turnkey then the 5% for capex, maintenance may be too low (and I agree with Cade that vacancy should be bumped up a bit too) - 8% is where I'd start with those three, being as conservative as I am.Who is paying utilities and associated costs? 

If you are planning to DIY your books, at least have a professional that understand RE industry to help you set up your books and explain the process for you, then work from there.

The quadplex seems like an ok deal, but is the apartment going to dictate my rents and what the tenants should expect to pay for utilities? 

It's main industry is refinery workers.

I understand that tons of residents have moved due to the plunge in the auto industry and the loss of jobs make it hard to want to come back. 

I believe the best way to go about this would be to utilize the HELOC as your new checking account and sit all of your monthly income inside it to reduce principal, which in turn reduces the amount of interest you pay and basically reduces your monthly payment every single month.

Being that you're in the other unit, you'd be paying over $2,000/month yourself - NOT including taxes, utilities and capex.