No, ultralights are single seat to protect members of the public:
"For example, the assumption can be made that a person who elects, without pilot qualifications, to operate an uncertificated vehicle alone is fully aware of the risks involved. This assumption does not hold true of a passenger selected randomly from the general public. Persons in the general public will likely assume that the operator has certificated pilot qualifications."
Also, not all airports allow ultralight operations.
To HN readers in general, here is how to understand how the FAA thinks, and why they will never deviate:
1) Passengers are assumed, correctly, that they cannot evaluate the risks of a flight, and FAA regulations must protect them.
That's why you won't see passenger drone flights in this century in the US, or any advertised "ride sharing" between strangers.
(The FAA has been slow on banning helicopter skid pop-out floats for sightseeing flights, but I predict that will change.)
2) That VFR and IFR flights must be physically separated.
That's why everything that moves will be required to have ADS-B out.
If you're involved in any kind of business model that opposes the above, it is only a matter of time until the FAA stops you. You're welcome to use the words "doctrine" or "never" when explaining the above.
"For example, the assumption can be made that a person who elects, without pilot qualifications, to operate an uncertificated vehicle alone is fully aware of the risks involved. This assumption does not hold true of a passenger selected randomly from the general public. Persons in the general public will likely assume that the operator has certificated pilot qualifications."
Also, not all airports allow ultralight operations.
https://www.usua.org/Rules/faa103.htm
Also, for insurance and legal reasons, no professional CFI is going to endorse you as a student pilot on an on-going basis.