I built this system for my mother with an old business pc running frigate. I used an old wifi router with ap mode available in the firmware that is only for the cameras. It’s a simple way to make sure the cameras won’t have internet access without relying on whatever router they may have. I added a second Ethernet port to the business PC because I had the parts, but for one or two cams you could theoretically do all over wifi. Install wireguard so you can manage it remotely. Then decide if you want to bother forwarding the ports and getting a domain setup, or if local only viewing is good enough.

For cameras, I used these amcrest ASH22-W which are good enough for the price. 1080p for $33

www.ebay.com/itm/314660333877

One thing to remember with these cameras- mounting them high gives you a bigger field of view, wipes out any possibilities of identification. The frigate models also don’t do as well. Doorbell cameras are better for that.