I don't really have the chance to get a raspberry pi camera. But I have tons of old phones and tons of phone cameras. Is there any way I can turn them into a camera that works with raspberry pi ?
I use a linux solution called 'motion' to stream from both Raspberry PI Cameras and from remote IP based cameras. If you don't want to have to build motion on your PI there is a image based distro called 'MotionEyes' which uses motion and has a nice web based interface so its simple to install and configure.
For your phones there is a iOS/Android app called 'Periscope' which turn out phone into a RTSP web camera. So you can stream video/audio from it.
Works very well and certainly for iOS its free.. https://apps.apple.com/gb/app/periscope-hd-h-264-rtsp-cam/id1095600218