I need some basic help on the differences between Blackberry models.

I spend every other month in Mangalore, India and Airtel is the local provider.

They offer a 8700g for there services . . . My question is this: Are there any other Blackberry models (lesser priced) that would have the same configuration as the 8700g that I could use in its place?

I will only be using the Blackberry for email purposes.

Are there inherent problems unlocking a used Blackberry?

Thanks for your help!