You have been given great feedback so far.
You need a plan. Read the
Cliff Notes and check out the
WIKI.
Once you get some of the background, you will have to decide on how to interface with the cams. Basically the choices are a dedicated NVR, a PC running cam software, like
Blue Iris, or if you have a NAS that has cam software using that. People on this forum, in general, have decided one over the other. Though I have seen posts of folks that use both an NVR and a software solution at the same time. I have a QNAP TS-251+ and, in the beginning, I used the Surveillance software for my cams. But eventually I did not like it and went with Blue Iris and a PC.
If you decide to go the NVR route, it is a good idea to choose all one brand of cams and NVR. Mixing brands will give you headaches. However, if you go the PC and BI route, then mixing brands of cams is fine. Personally I have gone with all Dahua cams. I believe in fit-for-purpose planning. Currently have over 21 cams recording, spread over 11 different models.
You need to decide on cams. But in order to do that, you need to understand what you want from the system. And I mean specifically, not just 'I want to be able to monitor the house'. What does that mean specifically? Front door coverage? Back door coverage? Do you have your cars parked on the street or in the driveway? How are you going to get ethernet to those locations? So before buying cams, define what you want from the overall system, and then where do you need cams to achieve that overall plan. Once you have defined where cams need to be, you need to define what each cam's job is. Then you define what attributes that cam needs to have to get the job done. Once you have that defined, you make the buying decision based on the merits of the cam satisfying those requirements.
Say you wanted to buy a house. There are obvious requirements that all houses should have, like a roof, locking doors, electricity, you get the idea. But you also have other requirements that are specific to your personal needs. Like maybe 4 bedrooms, two car garage, three and a half baths, etc. Well the same goes for your camera plan. And that plan will evolve over time as you gain experience and knowledge of how cams work. Mine plan is currently nothing like my first plan of two years ago.
Here is an example:
I want to be able to identify anyone that comes to my front door. By identify I specifically mean that I get a good enough face shot that could be used as a mug shot by the police. Plus I want to be able to get info on clothing color and types, any visible tats, and any voice or other sounds they make. I also want to be able to observe their gait and see where they came from and where they went after being at my front door. If a car was involved, I want make, model, color, and any other info including plate number. Oh, and all of this has to be done in both daylight and after dark. My front door faces South and has some issues with lighting and access. It has different lighting depending on time of day, time of year, and rain or shine. I have plenty of lighting on the porch and there are street lights near by. But the door is set back from the rest of the porch and I live on a corner.
I used a varifocal cam on a test rig (as defined in the Cliff Notes) to test different positions at different times and lighting. It became apparent that to get good face shots at the front door and it's approach, I would need more than one cam. I ended up with four cams at the front door. Two mounted at five and a half feet and two mounted at one foot looking up. This gives me a great chance of getting an unobstructed face shot no matter where the sun is shining from and no matter what head covering they are wearing. I then have a cam mounted on one of the porch pillars facing back towards the door so that I get the person leaving. Another cam mounted on the left side of the porch looking across the length of the porch to catch any access that does not come up the walkway. I also have three high mounted overview cams that cover the streets (I live on a 'T' intersection) so that I can see where the person came from and where they went. I also have two cams for LPR and another cam focused on the 'T' intersection for vehicle make, model, color, etc. That is twelve cams spread out over eight different models. Each model was chosen based on the requirements for that specific view/location.
An example of the requirements for the intersection cam:
Needs to be able to run in full color at night overlooking the intersection such that I can identify make, model, color, any damage/stickers, and any other identifying parameters from stopped or moving vehicles. This has to be able to be done in a distance range of 40-80 feet. Would be nice to get plates, but I do not expect to get that in low light from moving vehicles since I have dedicated LPR cams for that. Need to be able to get a good description of people walking through the corner 24/7. Now I just needed to find the right cam.
So I had three cams I had bought for installation in other parts of my home and tested them in the location I wanted to put this cam. One was an older cam that I had replaced from my driveway. This was an HDW5231R-ZE which is a 2MP on a 2/2.8" sensor with a 2.7-13.5mm varifocal lens. This was the top dog for low light two years ago when I bought it. By using this cam in that position, I learned that I needed more zoom than 13.5mm. I also needed better night color performance. I had a T5442TM-AS in 2.8mm fixed lens that I was about to install covering my front door and porch. This is the fixed lens turret brother of the Z4E. This test told me that while the 2.8mm was way to wide a view (which I knew already) the 4MP on a 1/1.8" sensor gave me great color night performance that allowed me to see all of my requirements. So that lead me to getting the B5442E-Z4E, which is an 8-32mm varifocal bullet 4MP on a 1/1.8" sensor.
Hope this helps.