Speaking from experience, there is very little margin in drop-shipping so you need to do a lot of volume. To do a lot of volume you really need to be spending on ppc ads. If you pour your heart into this and do about 1mm in sales a year you can expect to clear 80-120K. Just to warn you, to get to this level it might take 3 or 4 people working fulltime.

Making something and then selling it would be a better bet, but therein lies the rub. Once you buy product you need to house it and eventually ship it.