fix Financial Interest and set new Vehicle Taxation based on buy price

ReallifeGamemode.Database/Entities/UserVehicle.cs

@@ -17,6 +17,8 @@ namespace ReallifeGamemode.Database.Entities
     public int UserId { get; set; }
     public User User { get; set; }
 
+    public int? Price { get; set; }
+
     public override string ToString()
     {
       return "Spieler Fahrzeug | Besitzer: " + GetOwner().Name;