geez... The thread title is...
Borrowing from a solo 401k
--------------------------------------------------------------------------
The one-participant 401(k) plan isn't a new type of 401(k) plan. It's a traditional 401(k) plan covering a business owner with no employees, or that person and his or her spouse.
These plans have the same rules and requirements as any other 401(k) plan.
https://www.irs.gov/retirement-plans/one-participant-401k-plans
Retirement plans may offer loans to participants, but a plan sponsor is not required to include loan provisions in its plan. Profit-sharing, money purchase,
401(k), 403(b) and 457(b)
plans may offer loans. To determine if a plan offers loans, check with the plan sponsor or the Summary Plan Description.
https://www.irs.gov/retirement-plans/plan-participant-employee/retirement-topics-loans