Yes, you can run multiple businesses with one CRM Plus account.

Let's consider the following scenario. 

Derrick has two companies Zylker Travels and Zylker Industries. He is currently using Zoho CRM Plus plan for Zylker Travels. He wants to use Zoho CRM and SalesIQ for Zylker Industries and wants to add this company to his existing CRM and SalesIQ accounts in the same CRM Plus plan. 

He can do this by creating multiple page layouts in CRM and assign set of users based on his organization's requirement. To know more about multiple page layouts, click this link. For SalesIQ, he can create multiple departments and create multiple websites and embed the website code and associate appropriate departments to the corresponding website and provide access to his agents. In this way, he can manage both his business with one CRM Plus account.