How many devices can I manage on one account?

I'm trying to get all of my construction inspectors to use iPads for their daily inspection work.

How many iPads can I have syncing to One iTunes account? There wouldn't be many purchases after we get the adobe expert bought and a couple other apps for them to use. It would be mainly for performing updates and backing up photos.

I don't want our IT guy having to keep track of 20 different iTunes accounts if possible. Personally my iTunes accound has my MacBook pro, iphone 5, and iPad, so I know 3 devices works fine, but what is the limit if there is one?

Thank you