Most marinas do allow living aboard your boat. When living on a boat at a marina you will live somewhere that has many features of living on land, but living in a marina has some other things as well.
The Pros of living at a marina: living on a boat is usually more affordable than living in many types of living quarters that are available to live in; living somewhere with less living space will also be cheaper. The price for the size of living spaces can vary greatly depending on many factors such as ocean proximity and access to amenities etc. Living in a larger populated area will typically be more expensive than living outside of one.
Most love living aboard because it allows you to live on the water. Many people enjoy living beside or living on the water, but living on property by the water can be expensive depending on location and what kind of access to the water it comes with.
Living in a marina more often than not offers some basic living necessities such as showers, bathrooms, laundry facilities, electricity, and sometimes wifi service depending on your living arrangements.
The Cons of living at a marina: you will be living in a smaller space depending on the size of your boat and your slip. Docks can be located in very tight quarters and you may often see or hear people coming at going at odd times. You will more than likely have less privacy than living on land.