Yes, you can do this. If you have a rough idea of how many cameras you will be using and may want to add later this will determine the size of the POE switch you will want. If you are going to be looking at some of the higher end PTZ, you may want a POE switch that supports the newer standard(s) as well as the older ones (at, af, bt). I use the Ubiquiti USW-PRO-24-POE Gen 2 switch, with CyberPower CP1500PFCLCD PFC Sinewave UPS System, 1500VA/1000W, and Cat7 Outdoor Cable Triple Shielding SSTP Ethernet Cable. All of my cameras have the SanDisk 256GB High Endurance Video microSDXC Card installed in them. I have several UniFi in-Wall HD Wi-Fi Access Point (UAP-IW-HD-US) that I also run from the switch.
However, you are free to use whatever hardware you desire!
Highly suggest having a UPS as it has saved me many times with power flickers/outages. (Both for my computers and networking equipment.)
Highly suggest that the camera are on their own network (or hardware) and that network does NOT connect to the Internet. My switch above is connected to a Raspberry Pi4 to assign a static DHCP IP to each camera. Later if I want to/need to, I can put a USB to ethernet in the Pi and connect that to my normal network and use the Pi as a NAS for recording the camera feeds. As for watching the feeds on the phone, there are several programs that would be able to do it. I like TinyCam Pro and paid for it. For me, it was well worth the money.
-------------- I do not work for, nor get paid to advertise or any other benefits. Links are provided just to show exactly what I use. I highly suggest doing your own research to find the equipment that best suites your needs and budget. -----------------------
UniFi in-Wall Wi-Fi Access Point (UAP-IW-HD-US)
Amazon.com: Ubiquiti USW-PRO-24-POE | Unifi Gen 2 10 Gigabit Switch: Computers & Accessories
smile.amazon.com
CyberPower CP1500PFCLCD PFC Sinewave UPS System
SanDisk 256GB High Endurance Video microSDXC Card
Cat7 Outdoor Cable
UniFi in-Wall HD Wi-Fi Access Point
Amazon.com: Ubiquiti Networks UniFi in-Wall Wi-Fi Access Point 802.11AC Wave 2 (UAP-IW-HD-US), White : Electronics
smile.amazon.com
Ubiquiti U Fiber Multi-Mode SFP 10G - UF-MM-10G
OM5 Multimode Duplex Fiber Optic Cable (50/125) - LC to LC {Fits SFP above}
Unifi Dream Machine Pro UDM-PRO
Buy Ubiquiti Networks UniFi Dream Machine Pro All-In-One Enterprise Security Gateway & Network Appliance: Switches - Amazon.com ✓ FREE DELIVERY possible on eligible purchases
smile.amazon.com
Seagate Skyhawk AI 10TB Surveillance Internal Hard Drive