I am able to afford the extra payments and was primarily wanting to use this capital to scale my real estate portfolio via BRRRR.

Is it worth the extra 700$ and additional time to try to capture an extra 25-50k in HELOC?

Take the extra cash flow and make a principal payment. 3.

Did you rent out the extra rooms or did it have an ADU of some sort?

If you are going to miss and extra 6-9 months from a pandemic every 30 years shouldn't you factor in an extra 2.5%ish to your vacancy/non payment rate?  

I've seen scenarios where the appraisal came in much higher than the purchase price and the lender agrees to add an extra 5% of leverage.

We talked to one lender about refinancing our other investment property at the same to gain extra cash, but with that lender's higher construction reserve requirements we're still short.Anyone tackled this problem before?

I'm thinking of leveraging Airbnb to make extra income off the property to pay the mortgage by renting rooms.Any suggestion when it comes to Airbnb?

Does it make sense to get a HELOC first (100K max, 5 years at 5%), use that 100K (or less) as a down payment for a multi-family...Then do a COR on the duplex to pay off the HELOC + have some extra cash leftover to buy another property or pay down debt?

If you have some extra time and want to learn more about RE, getting that isn't a bad idea.