@Jordyn Ohs pay off/down your Heloc aggressively and/or look into DSCR loans for future acquisitions.

Got an equity line of credit and borrowed from it to pay cash for the property.

Went on to purchase additional rentals so tenants can pay down the loan and I build equity How did you find this deal and how did you negotiate it?

The current renter is paying 2600 for the whole house, but when fixed up a bit, the upstairs could likely fetch 2700 and the basement could probably get 12 or 1300.

Hire a college students/or architect from other countries who can do 3d rendering at a very affordable rate (I pay $200 for 4 first time super realistic 3D renderings of the exterior, repeats are even cheaper) and do a number of elevation studies before you down select your exterior paint and finishes.  

He pays seller's note ("outside" loan), and then the seller turns around and pays his loan ("inside" loan).

This seems unlikely in the long run. you are forgetting that someone is paying down your principal for you so you need to take that into consideration. 

If this is what sub2 is, then why are people paying tens of thousands of dollars to learn this process?

If you don’t have HOA or pay any of the Utilities. …..now the problem is in the Tulsa area that deal that rents for $2000+ mo and can be purchased “all in” for $150K is much harder to find. 

You can probably try this yourself with a letter or maybe even a phone call.If that doesn't work pay an attorney $400 to write a letter.