Is that interior lot line assumed when a duplex is built, or is some kind of formal process needed?

This will vary property by property and area by area, but in area not only do you have all the city/county level planning: access, traffic counts, density requirements, unit counts for school districts, sewer capacity, etc, but you also have neighborhood councils which will have additional level of say in final design, scale, unit counts, uses, etc.  

You mention you have no experience in these types of parks and your first deal you want to take down 100.When I was working for a GC we did a condo project for a developer who never developed a building before and he sold his company (it company) and used the entire amount to develop real estate.He ended going bankrupt because his inexperience with his experience and his designers and every mistake they made was multiplied by 150 since that is how many units there were.

Because new designs of rings will attract a lot of customers.

Mitch - A Good Strategy however; Can an ENTITY (your corporation) be designated as AIF - Attorney in Fact for INDIVIDUAL borrowers who's loan is being paid off?

I have never had to do a full gut on a home yet, mainly just flooring, paint, appliances, and interior work.

Should we do this or would it be better if we designed a postcard online to send out?

I replaced a broken railing mount for the interior stairs because a guest noticed it was cracked.The bottom line is to setup processes for yourself (or handy person/inspector) to go over your rentals a couple of times a year. 

BiggerPockets is full of resources designed to help you along your journey, whether you are just getting started or a seasoned investor.

To much money left over-  so you set up your trust and have money designated for donations, have your lifestyle covered, no kids, no spouse.