I have been reading in the Community about single lookup field, multi select field, subform, accounts & contacts, etc... but not sure what's the best way to accomplish what I need and any suggestions are appreciated.

Up until now, I was saving both users' data in 1 Contact record (using Phone number, Other Phone number, Email Address, Secondary Email address)... but I am starting to use campaigns and would like to send to both.  Therefore, I need to have each person in a separate contact with their correct first and last name.  However, for estimates and invoices module, we need to create a record (let's say an estimate) for both users together.  Anyone else accomplished this? What is the best way?

I was thinking of using Accounts, and having an Account Type that will differentiate from Household accounts and real Contractors (B2B)... but not sure I have thought about all the impact that can cause.

We currently have Deals for Accounts, but for Customers, we just have the quotes directly linked, without Deals.

Please guide me!!

I think in summary, my requirements are:

- Each user record has their own data (their email and phone #)

- Ability to create 1 estimate / invoice (Zoho Books) for both users

- Ability to mail both users (1 mailing ad goes out to address for both users)

- Ability to email them separately (email campaign sends to each one separately)

- If approach is to use Accounts, need ability to differentiate B2B and B2C

I have to think about how any customization will impact the integrations with Zoho Books, Zoho Campaigns, etc.