Knocking out that student loan debt will help a lot I'm sure.

@Nana QwequBanks also consider other factors like the debt coverage ratio depending on the type of loan or the type of property you’re trying to buy.

I have excellent credit and pay off all debt each month.

So knowing it's all cosmetic eliminates all contractors.

But again, that rental should always cover the debt service and make a profit for you.

Also the new loan will be counted against your debt-to-income ratio so if you're already close it could send you over the threshold. 

If you use a HELOC on your primary then the HELOC payments will be used with the Debt-to-Income for the new investment.

As I’m looking, my main concern is vacancy, since if I can’t get tenants to rent by the room I won’t be eliminating my housing cost.

Since you are in full time RE now and wanting to put debt on the homes, the outcome of the cash out refi will likely come down to your personal financial statement and income. 

@Susan Maneck - Yes, eliminating your rent can be a huge form of "yield", living in your property gives you huge tax incentives upon sale and in New York you would rather avoid anything over 4 units due to rent control and rent stabilization complexities as a newbie investor.