This is just one of the regular phone calls I receive. There is an old saying for that : Buy cheap buy twice...
Quick list to check on quotation from any firm or before purchase from online store, shop:
System type: TVI, AHD, IP, Variable or fix lens, Viewing angle, Resolution, Night vision, Light pollution, Size of the hard drive, Load on power supply, Product support, How easy is to operate it, Remote viewing on the phone, (Dynamic or static IP)
There are several professional brands like HIKVISION, QVIS (and many others) which are designed to work for long. Please, choose quality. It's worth it.