Cameras
I started with a few cams, added more, added more, replaced some and upped the quality, etc. Then I upped the quality further by buying a new DVR. So now I have a lot of $$$ sunk into cameras and a DVR. I think it has been worth it.
But, technology has changed, and your biggest choice right now is whether to go with "IP" cameras or traditional CCTV cams. With high quality and expensive IP cams, you can install one or two cameras and cover as much area as a LOT of traditional CCTV cams. By their nature, these are viewable over the internet as they have a built-in web server. And the quality is much, much higher than typical CCTV cams.
I would check out the VideoIQ dome cameras that have a built-in web server and built in NVR license. They are maybe $1,500 per cam, but the advantage of a LOT higher image quality and the simplicity of installing and maintaining only two cams might appeal to you. If I started fresh today, I would only use the much higher resolution IP cams like the VideoIQ. Another supplier is Mobotix, although their cams look a little weird to me. The Mobotix have a little better nighttime performance than the VideoIQ.
You'll have to make the final decision, but I would definitely evaluate the choice between IP and traditional CCTV. IP cams have a lot of momentum right now.