SD401K vs SDIRA and personal use of vacation property

[Sandy Blanton]

I've searched exhaustively but can't find clear answers. I understand that a SD401K allows one to manage their own rental, do their own labor on repairs/etc whereas a SDIRA won't? Where can I find the specific regs on this and any other differences between the two (401k vs ira)?

Two friends want to buy a vacation unit with their SD401K's, 50/50 ownership. They want to use the unit about 25% of the time. Is this feasible? If not, what if they paid market rent through a rental broker? If still not, what if they bought/owned the unit using 12.5% each personally and their SD401k's own the other 37.5% each? Thus accomplishing a personal ownership for the 25% of the time they'll use the unit personally.

Thanks in advance. Steven Hamilton II