My husband recently installed both inside and outside cameras. They use a DVR recorder and tapes in a loop. The size of the hard drive determines how many days is stored. He said he wouldnt go with less than 500GB. Also depends on how many cameras you would use. Its a good idea to have extra channels available on the DVR for future add on.
I asked him your question and he said it depends on your ability. The quality of camera vary so greatly that if you buy the system and dont like it your basically stuck. A person that installs this all the time will know what your looking for and will be able to pick the right equipment.
You want a good amount of infrared illumination for nighttime to get a good quality picture and distance. Its a hard decision to make to use the right equipment as a layman.
If you want to look around check out
http://www.specotechnologies.com/
They wont sell to the public but they make a good product.
Get prices from all sources and do some research on the info they give you. Get references too.
If you have any questions - just ask.