Individual 401(k)s will have the same withdrawal rules as regular 401(k)s. The withdrawal rules for a Self-Employed 401(k) are identical to the rules for a traditional 401(k).
If you want to avoid a 10% early withdrawal penalty, you’ll need to keep the money in your account until you reach age 59½, but if you separate from service after 55 you may be able to make withdrawals penalty-free.
If you really need the money early, certain exceptions for disability, medical expenses, 72(t) annuitized distributions, and plan loans can allow you to sidestep the penalty. Withdrawals for any other reason, including hardships, are still subject to the penalty.
Even for the exceptions listed, you will need to read the fine print. Income taxes will be applied no matter when you decide to withdraw.