I want to create a customer and service manager for a customer. I recently discovered Odoo. Due to the characteristics, the server will and must be hosted locally. 

The questions is the following :

• if I pay the subscription the time of the configuration and the deployment. Would I need to continue to pay for the customer to benefit from the subscription. Knowing that EVERYTHING will be local. 
• Could I just pay the subscription punctually to have the latest update and bug fix. 
• Will this have an impact on the number of users and its operation?

Cordially