If you go the HELOC route at any of these credit unions, you should be able to get the $24-$48K you are looking for. 

So glad you've already plugged into the Bigger Pockets podcast - that was a huge source of education for me when I first started.You mentioned that you had solid mortgage brokers lined up, but if I could add from experience...I would recommend that you talk to multiple lenders (banks, mortgage brokers, credit unions, etc.)

The terms you can expect will vary based on your experience, reserves, and credit scores and of course the property details.   

With good credit and a low DTI, youd probably get about a 4.75% or so right now.

Are you in charge of background checks- do you credit and criminal, other states> do you verify, etc.What happens in a hurricane when they can't go in the house for 2 weeks?

Can I report to a credit agency in MA?

I am actively working on raising my credit score and my personal savings so that I can get a head start on financing.

We are researching home equity loans, home equity lines of credit, and the possibility of refinancing our current mortgage to free up the cash needed to make those improvements and make the down payment on the multi-family unit. 

Venmo allows you to use a bank account or debit card for free (they'd charge 3% fee if using a credit card). 

Credit low only due to card utilization.