There are many types of different security systems, and they all depend on personal preference, budget and the area you live in, and you would also need to take into consideration what you want the alarm to do when it is triggered.
Bells-only alarms, which makes a noise
A speech dialler system would automatically contact you or other listed contacts once it goes off
Monitoring contract, where you pay a company monthly or annually to take action or call the police if the alarm goes off
Maintaining a burglar alarm can aslo bring the cost of having a security system installed up, but you're usually able to sign a contract with the company, which would check your alarms once annually, or twice if you have a police monitoring contract. Having maintenance done is also a requirement for some home insurance.