What research have you done already? Have you narrowed your BB choices down to specific models. Do that and you will probably get more assistance. A little homework on your part tends to g a long way on nay Forum.
You will need a BB data plan for all BB related services such as WiFi, email, BBM, BB Browser etc. Don't think SERO is an option. Don't use SPRINT so I can't say for certain.
Plus, I am not 100% certain, but I think the Mac version of Desktop Manager requires Mac OSX 10.5 or higher.