for those who do not want or do not have money, just keep doing the events of episodes and collecting coins for the cars.
You will also have an achievement making a 20 garage level that will take you much longer.
every day you receive a free car and even if that duplicate sale (the more you advance your garage level, the more you see duplicates) you received tickets for the car that got ex = 300x street class or 300x street retro