To get a camera with RTSP or ONVIF (video stream output) support, you look at the specifications of cameras that are available for sale. Web search engines should be helpful for this pursuit.

To get the surveillance functions of your camera streams (recording, alerts, etc) you install software on the Raspberry Pi that aggregates and records / analyzes the camera feeds. Zoneminder, Shinobi, and Motioneye are some examples of that kind of software.