The seller can often sell a property that can not otherwise be sold, financed, or sold for enough to pay off existing mortgage or obtain a higher price by selling Sub To, or Sub To wrap/owner finance.  

Received access to mortgage portal to ensure all payments are made (including escrow).Anything else here I should do or not do if acquiring for the long-term?

You technically do not have to replace the mortgage. 

As I am seeing 1.2 or 1.4 million 2 family house and not sure if its even going to cover the mortgage or not with 25% done.

I am guessing the beach houses were usually purchased and rented with a goal of “free” family vacations being paid for (along with mortgages) by rental income.  

What or who do you suggest I speak to or learn from to better understand my options for mortgages?

While still profitable, I’m exploring better opportunities and considering multifamily (MF) properties.In my search for $1M properties (with $150K–$180K down payments), I’ve found that the NOI often matches the mortgage payments, leaving little to no monthly cash flow.

Sounds like you have thought out a lot of this, but maybe also hold a competition with a cash prize at your closest architectural and design school.Can you build it cheaper than someone like this?  

Louis Fed shows the delinquency rate on residential single-family mortgages, and proves there's a way to spin this data to show that delinquencies are increasing rapidly.

🤔For me, each $800k of mortgages carried generates $3500/mo or $41,000/yr as an example.