Can multiple people (e.g., passive investors) share access to the same real estate bookkeeping data/account?

Yes. The system supports what's called multi-tenancy in software terms — multiple people can have access to the same underlying dataset. One use case described: a person acting as GP (though not legally the GP) for several LLCs with passive investors can give those investors direct access via team views, so an investor asking about bank balances or financials can log in and see them directly rather than requesting reports.