The benefits of joining a gym according to me are -
there is a structured environment for workouts... u feel motivated by watching others do....
u get ur own support group at the gym..... making Friends at gym is a great way to stay motivated.... meeting them on a regular basis u can learn a lot.
there is a variety of equipments available so that u don't get bored with one particular type of cardio, like treadmill, cross trainer, bike, arc trainer, rowing etc.
u feel committed to go (because u already paid for the membership u might as well utilize it).
strength training is also safe since u can hardly go wrong with machines, but doing free weights at home, u hv to be really correct with the posture otherwise u can get muscle strain