My concern is the current lien holder (Navy Federal) being notified of the second lien (not in the original purchasers name obviously) and then calling the note due.

I believe you'll find the American system of land title recording is based on English common law, except for Louisiana which is also is based on French law, so it's been around for a while and I doubt it's going to change anytime soon.My point about the body of law is simply that with title insurance, insureds and insurers have a pretty good understanding of where they stand under the contract, not so much with an AOL. 

I lived in N Charleston for 9 years while I was in the Navy. 

Located right in front of a large navy base.

I love that you are in Jacksonville because you have a large military concentration there with the Navy base.

It's a very affordable Florida beach market relative to the rest of the state of Florida & it is home of the US Navy's Blue Angels over at NAS Pensacola.I'm happy to discuss this further with you if you're interested in seeing my AirBnB for context & if you would like to connect to hear more about what you've researched so far. 

On our main street site we got this very beat up 1860’s home which would be a money pit to be rehabbed; c'est la vie- (that’s French for its getting demolished).

Anyone from a housewife with no work experience to a former Navy enlisted sailor can become a realtor in 8 weeks and THEN help a Buyer or Seller make decisions on the most expensive asset most people will ever own. ( Think about that for an hour or two) The real purpose of Real Estate School is to familiarize a prospective Agent with the Laws that the BROKER must follow and keep the BROKER out of trouble. . 

Weve had a lot of set backs from issues the seller didnt disclose or else id just have one customed made... instead putting in a french drain in and replacing our AC/heat came first.

One other thing to note about the h/st Trinidad corridor that often gets lost, its most of the area isn’t that metro accessible, when the city was growing and they hadn’t fully built out navy yard/the wharf/noma yet that was ok, but with the city shrinking and other newer more appealing options I do worry that the metro accessibly plus the age of the neighborhood will be a real long term issue.