Certified cars are hogwash that dealers invented to charge higher prices.
Used car prices are higher than they have been in years.
Best advise is compare like vehicles for pricing, craigslist, auto trader, nada, edmunds.com, kbb.com anywhere else you can find.
Get it checked out by a friend or ASE Master Tech (of which I was 20 years ago) with at least 10 years experience.
For craigslist shopping, an extremely clean car is usually a well maintained car ( in my experience but there are exceptions, dealerships always clean used cars so it doesn't apply for them) but get it checked out.
Whatever car you decide on research it online for common problems and repairs.
My friend has a 2007 convertible bug that the electric window quit working (not under warranty). It's a common problem with new beetles and costs around 800 bucks every time the dealer fixes a window. The new window motor has to be "programmed" by the dealer so it will be recognized by the vehicle. Welcome to the digital age friends.
Be careful, your best weapon is to be informed.
Never buy on the first visit.
Car salespeople are NOT your friends.
I've had an idea for an iOS app for used car buyers with a checklist but that's another story.
Good luck and have fun with it.
Sent from my huge iPod touch via IPF.