Let's say you're working on a few apps– do you make a new LLC per collaboration if you plan on turning the app into a business?
This is not legal advice.
If it is a serious business and you expect to be sharing equity with several people+, then yes, it needs its own LLC.
What I do with side project with friends is all under my main LLC, and we sign a little 1/2 page contract agreeing to share revenue with them 50% or what ever the % is. No need to pay filing fees for companies for every little app or website I make.