It can be, and we've done it. A self-directed 401(k) or IRA can hold investment real estate directly, and the deals that work best inside one are often off-market and creative. In one case, during a stretch of stock-market uncertainty, one of us rolled an old 401(k) into a self-directed account and bought rental units through an off-market deal where the seller wanted income without landlording and carried zero-percent financing for a few years. Once that seller note is paid off, the rents compound inside the account, tax-advantaged, until retirement age. We've also seen a client buy several distressed rentals inside self-directed IRAs when the market was down. They needed work at purchase, but with time and improvements the client built real equity, with a plan to fund retirement off that rental income. Two cautions. First, this takes genuine strategy and strict rules to execute: the account owns and transacts on the property, you personally can't touch or benefit from it along the way, and self-dealing is prohibited, so work with a qualified custodian and a tax professional. Second, we can't promise any property appreciates or cash flows the way these did. Underwrite each deal on its own numbers rather than on someone else's outcome.