If i buy a black berry?

hi i wanted to buy a bbm to talk to my friends which bb would i b able to buy with a budget of not more that 80 to 100$ n if i dnt want to get the blackberry messenger for 50$ a month would i b able to just download wattsapp?? plsss help...n wer can i buy it from if i live in clermont florida... n wat is the best plan for phoines i dnt understand how thta works wats the differnce at n t i dnt understand...