Different launchpads provide different conditions. On some launchpads I can have nothing on deposit at all, but I will be given the opportunity to buy new tokens for 1000$.
Yes thata true and on almost all of my experience most launchpads are like this, and required to hold tokens of their platform in order to join.
Because most launchpad platforms work according to the IDO principle. In order to be allowed to participate, I need to staking tokens of this site. IEO launchpads have roughly the same scheme.
Can I ask what platform you are talking about in which you could allow to invest on launchpad without staking any tokens?
Tokensoft, Coinlist, Republic.