You get 0% ROI for paying rent while purchasing will give you several benefits including asset appreciation, principal pay down, and tax benefits/ depreciation.Once you move out in a couple of years, you can re-evaluate the property to determine if it makes sense to keep it as a rental (in which case you still get all of the above benefits; however, the tenant is now covering the principal pay down), or sell it and capture the potential gains from the property's appreciation.

I can't help with a principal residence however.

During the 08 crisis I qualified for a HAMP loan mod that included a large principal reduction as my home was 50% below purchase price.

If you do not own a home, I would recommend you use the funds as a down payment on a light fixer which can serve as your principal residence for at least 2-3 years. 

Even if you buy in an LLC, it takes like five seconds to find out who the principal is.

Another advantage for a landlord with capital gains (or anyone else) is that the IRS views receiving the principal over time as an installment sale which can avoid a large one-time tax hit and being pushed into a higher bracket in a single year.

If I pay it off I immediately get 900 / m cash flow from principal and interest no longer going out the door.

This does not apply to prepayment of principal by you as the owners or if sold or if refinanced by the bank.· Collateral will be a 1st lien mortgage and GBSA on the real estate and personal property being purchased, respectively.

If so, you might consider setting up an installment sale from them to you, where the annual principal and interest payments are under the annual gift tax exclusion (which is fairly high if the “us” in your comment means that two or more of you will take title).   

I also don't feel the need to buy many doors or larger buildings; my personal goal is the most revenue, equity, principal with the least amount of tenants.