I'm thinking of buying a used copy of Fifa 13. I don't usually play online so I won't mind not having the online pass for that. But does the squad still get updated without the online pass?
I'm almost certain you won't be able to get the weekly squad updates. This is where a team's real life form reduces or boosts the teams attributes.
When you load Fifa 13 you will be asked to enter your Online Pass. There will also be an option for a Free 2-Day Trial as can be seen here. If you choose this you will have full access to all online features for 2 days.
You can download the proper squad updates during this period and you will have the squad update even after your 2-Day Trial is expired. This update moves player between clubs because of activity in the transfer market.
You could always buy an Online Pass if you really wanted to access squad updates. I think they are $10/£6.50.