Car Mechanic Simulator 2021

Go to the car salon and buy any car. There's a tablet near the wooden turntable on the floor, you can select almost any new car using the menu it provides.

The small hatchbacks are the cheapest with the Sakura Yaro being best for me at only 52k credits, just slightly cheaper than the Rino Piccolo.

The car was worth nearly 9k less as soon as I got it back to the garage and adding performance parts added value equal to 90% of the part value so there's no return on investment it seems.

If you just want the achievement, buy a cheap one as there doesn't seem to be a way to make money off buying new cars.