Is it a must for me to buy 3dsmax models? aren't those free downloaded models enough?

Im now still an interior design course student, and my friend asked me whether i wanna buy 3dmodels or not... erm actually must i buy those? or models will be provided by future ID firms? or should we just design ourself? orr...i should ask, does Interior Designers in big firms have to buy 3dmodels?@@