As the title suggests, vehicles should introduce various benefits or consequences for buying them. For example, super expensive vehicles give higher happiness buffs when driven than much cheaper ones, but at the cost of parking tickets (and towing) being MUCH more expensive to pay for, as well as needing to buy expensive insurance should the vehicle’s condition drop below a certain percentage (this can be avoided by taking it to the shop, but you’ll end up paying much higher prices for repairs than cheaper vehicles).
On the contrary, cheaper vehicles give little to no happiness buff when driving them and maintain the same features as they do in the current version of the game (0.4), BUT they are cheap to fill up with gas and have repaired, and insurance is a FRACTION of what it is compared to the luxury vehicles.
This is merely an idea that can be expanded on (or altered) by the developers however they see fit for the direction of the game.