Here are some things for you to look at.
You can use a series of web cams. Link them to your computer and use it as a DVR. Using web cams would be a little cheaper and just as good, and if they get stolen your not out a couple hundred.
http://www.newegg.com/Store/SubCateg...&name=Web-Cams
http://www.newegg.com/Product/Produc...7&N=2000290277