A 3/1 built in the early 1900s that has fallen into disrepair over the past 20 years and in needs of a full gut. 

I was looking to have it convert to a long-term mortgage and eventually cash out refinance to build a second duplex once enough equity built up 

You can hear real-world examples of how others have built their investment portfolio and (hopefully) learn to avoid their mistakes.4.

In a Seller Financing deal, once I start paying the seller the interest-loan + mortgage, the equity being built should goes to me and not to him correct?

You'll want to learn about the ins/outs of any HELOC you take as they are not built the same.

Triad consists of 3 cities Greensboro, High Point, and Winston-Salem.This area has seen tremendous growth in the past few years and I can see a lot of out-of-state investors investing in this area.Here you can still get a nice 3 bed/2 bath new construction or SFH built after 2020 for the 270-300k range and expect to get it rented for LTR for at least 1800-2300/m. 

I’m very grateful and lucky my investments have built so much equity and capital but I would like to move it into monthly cashflow so I can work away from a w-2.

Taking that step from theory to practice can feel daunting, but you've already laid a strong foundation by educating yourself.I’ve been working with real estate investors, particularly in the Indianapolis area, helping them find and invest in multi-family properties.

Built 1917, full reno 2022. 

We have MANY fail safes built into the operating agreement that would help prevent what you are going through.