I would structure this as a 30 year loan at 3% interest + principle with all the proper arms length paperwork.  

While we still want to live by this principle, we feel that paying all cash for all of our rental units will simply take too long.  

Or should I take advantage of my current monthly payment and pay extra towards the principle which can help me pay off the property sooner.Thanks!

I'm going to paraphrase here:"COMMONWEALTH OF MASSACHUSETTS LAND COURT DEPARTMENT OF THE TRIAL COURTORDER OF NOTICE TO: (Previous owner's name), and to all persons entitled to the benefit of the Servicemembers Civil Relief Act; Wells Fargo Bank...Asset-Backed Pass-Through Certificates...claiming to have interest in a mortgage covering real property at (address), given by: (name) to (mortgage company) dated May 2005...and now held by Plaintiff by assignment, has/have filed with this court a complaint for determination of defendants service members status...If you object to the foreclosure of the property above then you or your attorney must file a written appearance and answer this before OCT 31, 2016 or you will be forever barred from claiming that you are entitled to the benefits of said Act"Now, forgive me for my ignorance, but is this just a foreclosure notice?

If in ten years time you are not where you want to be as a real estate investor, if you haven't achieved your goal of not needing a job, if your properties are barely generating any cash flow, if you seem to be acquiring more properties and less equity in them, it will be because you spent your time on "motivational" education and searching for the elusive "technique" that will lead to riches, rather than acquiring a genuine real estate education, one that includes the theory of property ownership, real estate finance, real estate law, property management and investment principles.  

The Reit or whatever investment vehicle that part does not matter as the principle is the same regardless.

It depends on your goal and objectives.

It wasn't clear what the objection to PL's was other than you seemed to think a deeper discount means a better deal.  

When acquiring these old gems, or objective is to improve their energy efficiency by a minimum of 50% (40% on newer, post War houses) while updating the building to provide modern, healthy living spaces for our tenants.  

Option to pay towards principle after minimum monthly payment is met.