Reply to acapella or not

i've just started listening to dj's, i started researching and practicing my transitions as well as beatmatch, and looking at tons of tutorials , i have the basic numark mixtrack with traktor pro to learn the basics..
is there a way to just have vocals without a track playing in the actual music or would i have to go out and buy the acapellas, oh i wanna use it for effects, or transitions... can anyone shed a little light on that area for me please...
what other tools would be needed to make a pro style mix?