Power lifting requires practice of technique to win. However with just body weight and the right technique to make it better you can get as strong. Few people try this though as the good body weight exercise is hard.
Though power lifting can substitute rocks which are easy to "make" at home. (you cannot maintain perfect form with rocks though so you won't win competition, but if strength is the goal rocks work)
Don't get me wrong, I'm not against a good set of weights, if you want to buy equipment I'd put good weights at the top of the list of equipment to buy. However you don't need them if you get creative with body weight and are not trying to win competitions (unless the competition is really poor, you need to practice with the right equipment to win).