Plenty of people do have 10-20 unit and work thru it, you just need to think it thru and have a plan if you don't want to do all the work. 

I plan to utilize some cash, margin loan, 401k loan, and a HELOC as a down payment.My first house hack (now an out of state investment) has a Zestimate of $530K, and I have $266K left on the loan.

The Chicago Association of Realtors'® specifically state "When you become a Dual Agent, you owe equal fiduciary duties at that point to both parties in the transaction, and you lose the ability to negotiate for, strategize and advise either one."

And my #1 issue is I don't see any actions to address this in a meaningful, market specific manner. 

I’m planning to do this for 3 multifamily properties all located in MA, each ranging from 2 to 4 units.

Yeah that sounds like a good plan!

I plan on renting a unit and probably getting a roommate or two in my unit to maximize cash flow early on.

If you have specific questions about property management, I'll be happy to help!

You would need a premium plan. 

Would love to learn more about this flipping plan you have and get you connected with anyone you may not already have on your team.