I've been reading along with this thread but hav not commented yet. Cameras is a topic that can fill pages. I have been researching this myself for some time. Here's some things that I haven't necessarily seen addressed:
IP Vs analog cameras. There are differences, but the #1 difference is resolution. IP cameras have the ability to have much higher pixel count than analog cameras do. That is not always necessary. If you are covering a small choke point, an analog camera may have plenty of resolution to show faces clearly. Analog cameras tend to be better in low light and often (though not always) at night. Analogs are generally much smaller too, so can be concealed in tight spaces. But you pay for resolution, bigtime. IP cameras are always more expensive, and often several times more, due to the resolution and other features.
You can mix camera types, though it seems to make sense to go IP for the system backbone. There are converters that make analog camera signals into network signals so you can feed those into your network, if you want or need them.
Recording. Systems in a box that include cameras and a DVR/NVR are almost always crap and should be avoided. Dedicated DVR/NVRs seem like a poor choice to me as many require proprietary hardware. I believe the better choice is NVR software on a dedicated PC. You basically need to create a separate network in your house for IP cameras, as they can consume huge amounts of bandwidth. You get a few cameras going, and it will bury a home network and you will lose frames, drop connections, etc. You very quickly get into the need for gigabit ethernet switches, which are not too crazy expensive anymore. There are some decent software packages out there, but Luxriot seems to be the best bang for the buck. A commercial grade system with reasonable costs. Get a decent PC (used or not) and XP Pro for an OS as your server. Win 7 uses too much memory and resources for this application. With software like Luxriot, you can log into the server remotely even from your smart phone and watch cameras. It can send alerts to you. Track motion. Scheduled recordings. Things like that.
This gets expensive very quickly. If you try to do it cheap, you will find that when/if you need those images, they will probably be useless as you will not have enough resolution or enough camera coverage to see what you need. It is like race cars - "speed costs money. How fast do you want to go?" Only here you will find you have just wasted money on a cheaper system as it will deliver nothing useful when you need it. You need to get good cameras, and frankly a lot of them to really be useful. You are better off starting with 1 or 2 good cameras rather than a raft of crappy ones. Then add as you can.
My $0.02