You might want to check out edmunds.com for reviews on various models.
Like others are saying the cost depends on what you're looking for. Want a ferrari? 50 grand should get you started. But if you want just a basic economy car you could find one for as little as 5 grand but it won't be perfect at the price. As long as the engine starts and runs who cares if the body is not flawless.
And it goes without saying set aside some cash AFTER the purchase in case you run into issues. ideally, see if you can have a thousand bucks to take care of unexpected problems. Even if you take it to a mechanic and go through a thorough test drive you just never know 100% if there will be issues or not. When I bought my car I had no issues for about a year until I started having issues with overheating and had to get the radiator replaced. And this was a 2003 crown vic with only 56k miles and had a 1,500 mile warranty.
Hope that helps and good luck with your purchase!
