Here’s Adam Bergman’s latest article from Forbes –
The self-directed IRA is a retirement account vehicle that allows investors to use retirement funds to buy alternative assets, such as real estate. A self-directed IRA is not a term of art and you will not find it anywhere in the Internal Revenue Code. A self-directed IRA simply refers to an IRA account which is permitted to be invested in traditional assets, such as stocks, but also alternative assets, such as real estate, precious metals and tax liens. In the last several years, the number of self-directed IRA accounts has grown significantly.
The Internal Revenue Code does not describe what a self-directed IRA can invest in, only what it cannot invest in. Code Sections 408 & 4975 prohibits Disqualified Persons from engaging in certain types of transactions. In general, as long as the self-directed IRA does not purchase life insurance, collectibles, or engage in a prohibited transaction outlined in Code Section 4975, then the investment can be made.