Are there limitations on products, clients, daily sales invoice?
You can add as many as you need 
There is one limit that applies to inventory items. This is currently set at 1,000. There are no other limits imposed on invoices, clients, suppliers, bank transactions etc.
We do monitor accounts so if we see very heavy use i.e. 10s of thousands of records being created in a short space of time we will probably contact you to discuss further, this is only to ensure we can maintain a smooth service for everyone else.