re: Can my brother self direct a 401k into my re projects

He works for my construction business. I am the owner not him so he doesn't have that coverage. However what he would be self directing into would be an apartment syndication outside and separate from our construction business. From what I understand a person cannot use his IRA to invest in projects where he is active. My brother would be passive here and using a 401 k and I'm not sure if any red flags would pop up.

On a separate note, a friend who has his own business with employees has his retirement funds with Merrill Edge and would like to move these into a QRP to be able to invest into this deal. I am unfamiliar with how this works? What would be the tax advantages over a self directed plan? Would this have any impact over his employees if he was to do so.

Any feedback would be most appreciated.