No, you cannot purchase cars from dealerships or any other vendors in Mafia 3. The game's core mechanics are centered around stealing vehicles. You acquire cars by simply finding them in the open world, commandeering them from civilians or rival gang members, or unlocking them as rewards for completing specific story missions. This design choice is intentional, reinforcing the protagonist Lincoln Clay's role as an outlaw building his criminal empire from the ground up.
When you enter a vehicle, it is automatically added to your personal collection. You can then access any car you've previously "acquired" by visiting one of your three underworld garages located at Sammy's Bar, the Barclay Mills safehouse, or the River Row safehouse. This acts as your de facto car storage system. Certain high-value or unique vehicles, often referred to as "Faster Baby" cars, are permanently unlocked only after you complete specific story missions for your lieutenants. For example, finishing a mission for Cassandra will add her unique car to your garage.
While you can spend in-game cash on weapons and upgrades, there is no option to spend it on cars. This lack of a traditional purchasing system differs from other open-world games but fits Mafia 3's narrative of taking what you want by force. The primary way to expand your garage is through exploration and progression, not commerce.
