My self-directed 401k investment strategies will be to flip cars and real estate

QUESTION: My self-directed 401k investment strategies will be to flip cars and real estate. Do I need to hire property managers to maintain arm's length transactions? 

ANSWER: With respect to real estate transactions, as the self-directed 401k trustee, you can manage the properties, just not get compensated for doing so.

As far as flipping cars, the self-directed 401k can invest passively in a company (e.g., a car dealership); however, it may subject the investment earnings to UBIT. Further, you cannot be the manager/president of the car dealership company nor an employee as you would fall under the 401k disqualified party umbrella.