I own a mortgage company, so I have my loan officers use this Fannie Mae income calculation tool for all business for self borrowers: https://singlefamily.fanniemae.com/applications-technology/income-calculator .

Over a 3 to 5 year window.Our self storage developments we expect a 400% COC return in 2 years.  

Before moving out, test different strategies, automate management (smart locks, cameras, cleaning services), and decide whether to self-manage or hire a property manager.

There are good relations with the neighbor so this likely wouldn't be terribly difficult to pull off, but I haven't ever developed a property from scratch so I would definitely like the opportunity to partner with someone on this to help ensure the success but first I want to finish the smaller property to have sufficient funding available if it is needed.

You could conceivably start with a 50-story high-rise development.

We've developed a solid plan to continue growing, but I’m looking to create systems that will enhance our efficiency and help scale our operations.

Where we fit into the "turnkey" model is that our marketplace specifically focuses on newly built properties or renovated homes in good markets with property management in place so you are not having to try to self manage from a distance or build a team on your own.

Quote from @Havital Miltz: Normally you would set the LLC in the state where the property is.You have no tax benefits for setting up an LLC, it is more a protection from lawsuits and going after your personal assets, however not a guarantee....As a husband and wife you do not need to set up a partnership - IRS has special considerations for married couples for self employment, you could also apply that for a rental...Hope that helpsA joint venture is available to any 2 people co-owning real estate for investment purpose as tenant in common  under Proc. 2002-22 (unrelated to marriage) but it can't be owned in an LLC together. 

Keep in mind this is a self-directed account and most are not.  

I have over a decade of experience in strategy consulting and in real estate underwriting for new acquisitions and ground up developments.