I am intrigued by this. I spent some time in the Carribean once or twice and recall a lot of properties having concrete block walls around the property or courtyard that are plastered, and often have broken bottles/glass embedded into the plaster while it's wet in order to deter people from trying to climb over the wall without a crazy ladder setup. Doesn't stop someone who's determined but it's enough to stop the casual/opportunistic person, or the person who wants to be subtle (and not carrying around a bunch of big ladders).

Here in the US security in terms of actual guards/people does happen but it varies so much that there is no single description I can give.

There are security programs you can buy as a subscription, much as you would with a phone or internet connection - these don't have a human going to every property, instead the home is provided a set of sensors that detect things like: is the door or a window opened while the system is 'active'? Was glass broken? A motion detector may detect motion and turn on a light, as an example. The motion detector and sensors are connected to a dispatcher for the security company, and depending on your subscription the dispatcher may contact you (the owner/resident) and ask if you are home, is everything OK, and so on. Or they may send one of their own guards, or just call the police directly depending on the provider, the neighborhood or town, the options you've selected, and so on. Some also connect your smoke or other "toxic gas" detectors and can contact the fire department on your behalf.

In my apartment complex we have about ten buildings. During the day maintenance and office people are around, but the property owner has a contract with a private un-armed security service to have someone drive and walk around the property at night. Sometimes I see the person come into the building, they might check the basement (storage, garage) and the lobby. Sometimes they just drive around and keep an eye/ear for suspicious behavior. The gate on this property is fully un-staffed, you use a keypad to enter a code if you want to get in -- but there are other properties that sometimes DO have one gate with a person (and a second gate which might not be staffed).

Sometimes a tall building will have a desk in the lobby at ground-level that accepts packages and mail, and a rotating set of staff that all the residents know. You let the staff know if you are expecting guests or service (eg. a computer repair person) and the staff can let them into your apartment if you're not home (but the person is expected). If you are not expecting anyone and a random person asks to get into your apartment, the staff call you and do NOT let the person enter the building without permission from the resident. They serve as low-level security in many regards.

Others have "in-house" security, especially larger or wealthier buildings or developments. My apartment office contracts with third-party companies, but "nice" places will sometimes employ security directly rather than contracted. That gives the property owners more control, and the security teams often know the residents by name and vice-versa which is not necessarily a bad thing (but you have to be able to afford that!).

And a lot of neighborhoods of all types have a "community watch" program with residents who voluntarily call each other and/or police. For instance, if I am on vacation next week I might let the other neighbors on my street know I'm going to be out of town. If they see someone or hear something in/at my house, they know it's not me and either come over to check, or call the police. You hide a house key under a rock, under a flower pot, stick it underneath something with a magnet, set it on a rafter - something like that. If there is a problem while you are gone a neighbor calls you (or the police call) and you tell them how to find the key. And if there are no problems then your house is still secure, obviously.

In an apartment building/property, the property owner or office will have a copy of all the keys, obviously, so hiding a key is not important unless you are asking someone to come into your house to care for a pet or water your plants (and then you give them the key directly); but for people who own their house/condo then what I have described is the common solution for lower levels of security needs.