Security set with RJ45 cams

everything Ralston18 said X2

a couple of finer points and my experience setting up a security camera system that may help you initially narrow down your search - i went with a Hikvision cam mini-dome https://www.bhphotovideo.com/c/product/1162391-REG/hikvision_ds_2cd2542fwd_is_4mp_wdr_day.html. I don't know what part of the planet you're in, but Hikvision and Dahua seem to offer the most bang for buck in terms of quality - forget D-link, Nest, etc - Dlink is way behind their competitors in terms of service and features. Hikvision and Dahua both offer excellent products ranging from the consumer home user market grade to full blown professional, including a $42,000 thermal imaging camera.

Problem with both Hikvision and Dahua, you'll find purchased from china or hong kong vendors, pricing is 60% of same unit purchased from your in country distributor - but purchased from asian market means warranty and tech support will be "iffy". My Hikvision ran $198 USD shipped - i could have gone with a lesser priced mini-dome but would have surrendered the resolution (2688 x1520) and two way audio capability - the unit i chose has the microphone built in, so i only had to provide an exterior speaker to allow 2 way conversation. The unit i purchased was for use by the entrance but it has a good view of the parking lot & street, and i wanted the resolution to be able to better read license plates if necessary. For the other units around the building, i've gone with a lower priced Hikvision with somewhat lower resolution and no two way audio - cost from a USA authorized vendor was $131 each.

I was concerned about chinese products having "back doors" in their software, but it seems an isolated system without access to the web is safe. One reason i went with Hikvision, before buying i downloaded their configuration tool software and the same from dahua. When i opened the dahua's software, while my malware/virus software had scanned them both and found nothing suspicious, when i open the Dahua software my system literaly sent flares up to the ceiling. I ended spending an hour running the spyware/trojan/malware utilities majorgeeks.com recommends. Found about six files buried deep in root files, with two labeled "DHCP xxxxx...." - basically "call home" files. The Hikvision software set off no alarms.

As to storage requirements, i was getting my feet "wet" with the first hikvision camera - and at 2688 x 1520 resolution, at 20fps, i was concerned about storage requirements. I installed a separate 1TB SSD to see what the real world GB daily storage would be. Initially it ran 12-13GB daily, but i found buried in the software the option to use "H.264+" encoding. Did some research and the consensus seems to be that H.264+ or H.265 generally reduces the file size by 50% without suffering quality or resolution loss. My experience is that the storage requirements dropped to 7+ GB daily on the one camera. Assuming 8GB daily per camera, with six cameras, 1TB is good for approx 20 days storage, which is beyond what i wanted.

One option to look for if you're building your own setup, is as Ralston18 mentioned, PoE cameras - ie, powered over the ethernet cable - it saves needing a 110V source at the camera. But it also means having a switch, router or NVR that offers offers PoE ports. BTW - The camera being PoE means it has the circuitry to receive 48V current, and reduce it down to the 12V or 5V the camera needs.

when thru setting this system up, six cameras ($850) + Trendnet 8 port (PoE) switch $125 i'll be right at $1000.
Then i've got to decide whether to go with a NVR ($300-$400) with it's own display or a small low end computer. FYI, the NVRs most come with PoE ports, so you can pull the value of the Trendnet switch out of the equation. But either the NVR or the small computer setup will not have access to the internet unless i want remote access to the cameras and want motion alerts.

if you want to keep it low budget, there are a ton of complete systems offered (Foscam) in the $400-$800 range - go thru them on amazon and check their reviews, and read the reviews for the same product on Newegg.com to compare reviews

fwiw

PS - the IR night vision every manufacture claims, i've come to the conclusion they all exxagerate the range capability. But irrespective, it's useless on a camera you want motion alerts from - mainly because the IR light attracts spiders and moths (i kid not). On my first camera, a NEST, i had a moth the size of the palm of my hand that at least twice a week was attracted to the IR LEDs which meant flying up to the lens and setting off the motion detection. Solution i found was, on the front entrance camera, i de-activated the IR lights (usually a feature in the software) and instead installed a 5000K LED light bulb. I found 5000K does not attract moths or whatever insects. The softer white (2700K) will. On the other cameras i will have to find IR lights i can install separate and away from the cameras, which is something of a hassle / expense. On two sides of the building, we have lights that remain on all night, not the brightest but enough - with an .01 lux camera (which all the Hikvisions are, iirc) i could read an employees name tag on his shirt at night at approx 60-70 feet distance.