The Big Idea Not all solo 401(k)'s are the same... and the differences can be very profound. Points To Ponder A 401(k) is an employee-sponsored salary deferral and profit sharing plan.  It can be both, one or neither of "Solo" or "Self-Directed" Solo 401(k)'s offered by stock brokerages tend to exclude all assets other than stocks, bonds and mutual funds. The law doesn't require a 3rd party custodian/trustee for your 401k, but some providers do Your plan will be more flexible as a trustee-directed plan than as an individual-directed plan... as long as you're the trustee! The expertise and availability of the provider of the solo 401(k) plan is the most important distinction Bryan's Recommendation:  Talk with Tim Berry for a Solo 401(k) that meets all requirements Resources Episode #247 of Self-Directed Investor Talk Free Webinar that shows how many SDI Talk listeners are receiving very large credit lines at 0% interest for their real estate deals or businesses.  Check it out here.