Your phone will work with any plan. You just need to buy a sim card in a TMob store, After activating your phone register in BB forums like Crackberry for free ringtones, wallpapers, games, etc. Do not expect all of the freebies you see in the Android Marketplace. You'll do fine to buy the flip phone.
Make sure the CL phone is active or that you bring an active tmob phone with you. Put the active sim card in the BB and see if you can make a call.
Have fun. I luv my flip!
The phone (voice and text) will work. But without a data plan you will not be able to use the BlackBerry-specific data services, not even on wifi. Likewise, there are some third-party apps that will not work without a BlackBerry data plan.
The 8820 does have wifi. So far as I know, T-Mobile allows BlackBerrys without a data plan to use wifi, unless things have changed. Some carriers do not. You may want to call customer service to verify.
You also should look at http://www.blackberryfaq.com/index.php/Buying_a_BlackBerry_off_eBay ... The article refers to eBay but it applies generally to any second hand BlackBerry.