Buying a used car - how old should it be?

I am looking to buy my first car and I don't really have a preference for manufacturer, model. It's just to be used for my work commute. I think buying a used car might be the best option financially, however I'm not sure about the trade-off between its age and price.For example, I imagine the older the car is and more mileage it has, it's more prone to having more frequent repairs needed, therefore spending less to buy it might not be the best financial option long term.I think that 3 years is a good sweet spot, but I don't know that much about cars and maybe some people can advise? For reference, I am looking at small 1L hatchbacks so nothing special. via /r/cars http://ift.tt/2sZ1PUF