Traveller needs help with Blackberry pick

It's a bit of a complicated one, any experienced travellers?

I travel through Europe and America constantly, using a normal phone to call and text with a different sim card in every country to make it cheaper. I want to keep this phone to call and text, and need to get a Blackberry for the messaging function and the internet function only.

1. Is it cheaper to have a prepaid blackberry so i can put a simcard from whatever country i'm in to use the internet and the messenger, or is it cheaper to get an abonnement and use the internet everywhere in the world through that?

2. Could I even get a not-simlocked prepaid Blackberry and put random international sim cards in it?

3. Could I even use the internet with a prepaid Blackberry?

Thank you for being so kind to help me out!