Buy both the fire and burglar alarms to prevent unnecessary losses.
To Catch a Burglar
The best place to put a burglar alarm is where visiting Sims enter and exit the Lot. This can also be an easy way to make some extra cash. Placing the burglar alarms indoors can be iffy because once the burglar starts running, the cop can't catch him. Placing the alarms on a wall segment on the corners of the lot will cause them to go off the second the burglar steps onto the lot. The burglar will get caught every time, and the policewoman will give you $1000 for the catch. (One more thing: Don't bother to call the police if you don't have an alarm; they won't make it before the burglar gets away.)
For more Tips & Tricks for playing The Sims, including Time Management, building Skills, and getting more money, click here.