Self Directed Solo 401K

[JIll B.]

I am self-employed with 1099 income. I want to open a self directed solo 401K so I can invest in syndications and other real estate. I have a 401K with my previous employer I will roll into my solo 401K. I was looking at E-Trade because I need the rollover option and I want a Roth option. Is "checkbook control" the same as "self directed?" Are all solo 401k's "checkbook control" or "self directed?" I'm having a hard time finding the terminology on the actual investment firm sites. I also want 401K and not self directed IRA because I want the Backdoor Roth option. E-Trade and TD Ameritrade are the only 2 firms of the 5 big ones that offer the options I need (rollover option and Roth option) but I can't see that they specifically allow for RE investing. Is that just a given? Or do I have to go through a 3rd party to set the self directed solo 401K and then have my investments held at E-Trade, Ameritrade, etc? Just wanting to make sure I set it up correctly. Thanks!