I run several companies with different colleagues which subscription best fit my needs?

I run several companies with different colleagues which subscription best fit my needs?

I run 2 companies in Belgium: www.alt-f1.be and www.amia-systems.com

ALT-F1 is a 3 persons company while AMIA Systems is a 4 persons company not including resellers (3).

I want :

1. to use one single account to manage my 2 brands
2. to share (or not) the prospects, customers, accounts etc depending on the situation
3. apply the same rule to other Zoho products such as invoices and Campaign

Thank you,

Abdelkrim