Consider how many hours of freeroll playing it will take to earn your first $50. Possibly hundreds of hours. If you want an example of opportunity cost, here it is....
If you really interested in learning some poker, I suggest that you instead deposit $50 and spend these "freeroll hours" reading all posts in the beginners digest and grinding $2nl on poker stars - you will quickly be making poker $$.

That being said, there are a number of players here who have built a bankroll from nothing. Most of them would agree that the $50 deposit approach is smarter.