two user access for turbo tax account

Can’t you just give them your username and password?  Turbo Tax Online is only good for 1 return per account.  

When you use Online TurboTax, you get one return per fee.  Each return needs its own account and user ID.   If you use the same account and user ID for a second return, you overwrite the first one and lose it forever.

https://turbotax.intuit.com/personal-taxes/online/

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596