When you say security system what do you mean by that? You’re lucky enough that this happens to be the field I work in.
if you mean security camera's
There are plenty of great security camera's availbe it depend on what you are looking for. battery, cabled, doorbell, nightvision numberplates.- Eufy
- hikviosion
- Dahua
These are all great option and not to harsh on the wallet. They are near indestructible if installed correctly and have great connectivity.
Alarm system's
This is a tricky one, depending on where you live and what the laws are it can sometimes be better to get it proffesionally installed. Here in the netherlands there are a heap of choices and if its installed by a registered company you can get a discount on your insurance( Sometimes you are required, but thats a different story) If this is the route you want to go here are a list of some great options: - microtech galaxy - ge advisor master - satel - riscoBUT if you are looking for something to just scare them off/detect when or if you have been broken into
there are plenty of options. You can buy cheap kits from aliexpress that have the same functionality just depends on what you want. Another alternative is to set it up yourself - you get some zigbee window/door contacts, PIR - motion sensors and vibration sensors (If you want glass break detection) connect them all to a hub with alarm feature. There you have it. A reasonably cheap alarm system. xiaomi aqara have some cheap sensors that have a pretty long battery life and is pretty good.