With this vehicle he will have virtually limitless investment options, including being a private lender.

I just want to know if that is possible with any of these deferred sales vehicles, and if it would fly with the IRS. 

This is a high foot and vehicle traffic in an up and coming neighborhood with a lot of development in the area.  

If you ask people where they'd want to live between the two places and you probably get 99% California.Of course, you're rightfully telling us that your situation is different to most here as those properties are primarily for your own use rather than as an investment vehicle.

They slept in their vehicles to save money. 

Additional highlights include an indoor laundry room, a separate 2 car garage with storage capacity, and a large backyard offering plenty of parking for vehicles, boats, or an RV.

In my market, my vision is to buy & hold with maybe a few flips along the way and be financially independent by age 50 (i'm 28 now).I don't want to get into a ton of debt (if at all) and my real estate law professor said tax liens are a unique vehicle for that strategy, but I don't know how they work or if they're riskier than I think they are.Anyone have any insight on how they work in Ohio, or success/horror stories in tax lien certificates in any other states?

The IRA LLC model has been around since the early 1990's and is quite solid from a regulatory viewpoint so long as you use the vehicle within the IRS rules.Specialty advisory firms referred to as self-directed IRA facilitators provide such services, which involves legal work the custodians themselves are restricted from providing. 

You should of course require a new application with full contact, employment, references, and vehicle information to be completed, and vetted, before you offer any new terms and agreement.

If you were making a shorter term investment (like a flip, versus a rental purchase), you might want to look at a different investment vehicle like a heloc loan where you might pay a higher rate on your borrowed money, but not give up your better rate on your existing mortgageHope it helps!