From Tycoon Gaming
The Garage is where you can spawn the vehicles that you have purchased from the Car Dealership.
Garages can be found all over the map, as part of Businesses or as a placeable Faction perk.
There are different types of garages available for vehicle spawning:
Do note that certain garages may have other vehicle types available, you can see the specific types by hovering over the garage in the pause menu map.
Special garage types may also appear as part of events.
In order to sell the vehicles that you have purchased, you need to switch to Legacy Garage first by navigating to:
M → Player Options → Interface Options → Toggle Legacy Garage. After that, the Sell Option should now appear in the Garage spawn menu.
Be advised that when selling a vehicle, you will only get 15% of the price back you paid for it.