In most places a carport that is not attached to the house is not considered to be a permanent structure.
When I lived in town and asked about the permit for a carport they said that they did not consider the carport to be a permanent structure unless I attached the carport to a house or other building.
Carports can be easily tore down and moved so they are in most places considered temporary structures.
Adding a carport may or may not increase your property taxes either depending on how they classify it.
If you need a permit to build or erect the carport make sure you get one and all you have to do is ask whether or not you need a permit.
In some smaller towns you may not need a permit to build or erect a carport.
In the small town I used to live in of around 200 people I could do anything without a permit including building a carport without the permit and nobody cared.
I actually asked if I needed a permit at the town hall and they said no that I could just build the carport without the need for getting a permit.
However in some other larger towns or locations you may actually need a permit to build or erect the carport on your property.
So it would be best to ask the town or city where you live if you do live in the city or a town to see if you need a permit.
If you do need a permit and you build or erect the carport without the permit they can fine you and even force you to tear the carport down.
But if you live out in the woods or rural then you do not need a permit and even then I would not bother with getting a permit when I live out in the woods or countryside.
I moved to the countryside a few years ago and build and do things like I want too and nobody tells me what to do.
It's very nice living out in the countryside.