Thank you everyone for the info. From this thread and from reading others I am definitely leaning more towards a used mac pro.
What specs should I look for? I want something kind of basic for now with the option of being able to add on more stuff later. For example I know you can add RAM so I would probably buy a 4gb of RAM mac and possibly add more RAM later. What specs do I definitely need on the computer (as in I cannot add it on later?) and what specs would be helpful to have right away if I want to run final cut pro.
Not all that related but would it be smart to get the apple care warranty on a mac pro (if i buy refurbished)? Or are those a bit easier to fix than laptops? Also, when buying used towers online, is there any way to check what generation they are?