The cost of basic CCTV is:-
Your privacy - basic systems are likely to be hacked or have known exploits, have no maintenance or software updates going forward.
Your internet - hacked systems generally become part of a botnet where they use all your bandwidth and grind your internet speed to nothing.
Your electricity - Fancy mining bitcoins for someone else? Even if your system isn't exploited to mine bitcoins, what use is basic when you need to use it in evidence.
Your time - it's likely DIY or basic CCTV will fail and have no support.
Your money - you could have put that towards something that would be useful in an event. Many people have gone basic and regretted it after an event.
I'd expect 4 cameras to be at least 1k if it's anything upto a spec worth fitting.