What are the self-directed real estate investment rules and prohibited transactions?

The Self-Directed IRA owner and disqualified family members must not benefit, live, or vacation at the property. All expenses and revenue must flow to and from the IRA.

Your retirement account is not allowed to purchase real estate you already own. The IRA and IRA funds must be listed as the buyer, not personal dollars.
You and other disqualified people may not use the property (see disqualified person list here).
You and other disqualified people may not perform any property repairs or improvements. Personally, a third-party must be hired to do any repairs to the property. You can still oversee and monitor workers hired by your IRA, do paperwork, managerial and office-like duties, but you can't do physical work or get paid any salary of commissions.
When in doubt, if you can easily remove yourself from the day-to-day business, it’s best to do so and use a trusted, non-disqualified person. Here is a list of acceptable substitutes.