ISP SET UP

Good Morning or Good Afternoon to your Tech guys – quick question please.
We are trying to set as an ISP to provide our clients (10 companies) within a small location with internet access. I have contacted a Telco company who provide us the service (Bandwidth) – we aim to buy DS3(45MB).

They have asked me of how many IP addressess do I require? And I am not sure what to say to them? Any ideas of volume of IP needed?

Please any help or pointer will do. Thanks