The type of property that i am most interested, is Single Family properties & 1-4 Multi-FamilyInvestment Strategy: Out of the options you provided, I am most drawn to rentals.

On my single family houses I hide a key . 

It depends on the number of Units, Residential or Commercial, Apartment Complex or mix of Single Family and Multifamily.Under 25 unit - Tenant Cloud, Rentech.Under 100 - Then Doorloop/Buildium.100+ - AppFolio, Yardi, Rent Manager.Apartment Management : Yardi seems to be wildly usedSingle Family ( Mixed ) - AppFolio seems to be popularRent manager has a good customer support team.

In most single family zoned areas, a single ADU has a value far less than the hands off cost to develop it.  

Federally (HUD), you are exempt if you have & self-manage three single-family homes or less, or a multifamily home of four units or less that you occupy one unit of.

Hi, I have a landlord's policy with Farmers Insurance; the rental property is a single-family. 

Some of the features I am looking for (most likely there is not 1 single vendor who has all this built-in, but more of a technology stack that integrates nicely)Would something like propstream, carrot, and kixie be powerful enough to get rolling out the gates and still be efficient in your eyes?

Has anyone had recent success finding a bank that will offer a Heloc on a single family investment property in Jacksonville, Fl?

Plus a contractor will ask for every single change that benefits them.

@Andrew Caton if money isn't an issue you should have no problem getting approved by a bank, it would probably be harder to get two unrelated people approved for a single loan than it would for you to get approved on your own.