>if you are not currently eligible to create a solo 401k, it is very easy to become eligible with a single dollar of 1099 or schedule C income the year you make it, and then it can exist in perpetuity

No, your scenario is not "very easy". No custodian is going to handle a solo 401k based on one dollar of self employed income (and 1099-NECs aren't issued for such tiny amounts anyway). You are also overlooking the overhead of maintaining a 401k, such as plan updates every time related federal tax law changes, or the potential IRS reporting requirements, which can generate significant penalties if overlooked.

Merrill Lynch is usually good about that sort of thing. You're right that you wouldn't _only_ have the $1 401k, but they're fine having a few phantom accounts here and there to execute your financial strategies, and they'll stay on top of inconvenient legal changes for accounts they know about.

yeah, in the 10 years I've had one, the compliance is just a notice from the "document provider", and a 5500-EZ document annually. the bank, brokerage and crypto exchange accounts have no monthly/annual fees.

OP can also just use the solo 401k's roth balances as a temporary holding place to then pass through directly to the roth ira

The expanded investment options are worth it alone. And the years where there is self employment income, the expanded contribution limit up to doing my own $70,000 employer match saves literal years of contributions off my life.

It's literally 10x what the IRA contribution guys get, and most of them are barely able to even reach the IRA contribution max.

There are more tax deferral plans out there too, I'm willing to do that compliance.