If I buy a used car with under 50,000 miles can the seller have the car certified at our request? Aprox how much does that cost

you don't specify what brand, so I can tell you what I know about how GM certification works. The car can't be more than 6 years old, and if the dealer is participating in the GM Certified Used vehicle program, they can certify it. The cost is approximately $600 plus any extra repairs the inspection requires (the inspection standards are higher than the normal checkover list). What you typically get for that is 12mos./12000 miles comprehensive warranty and a 5 year/100000 mile powertrain warranty which starts from the time the car is sold new. If the car is only a year or 2 old, it already has that 5 years/100k on it and it does transfer to the new owner (again, i'm talking GM here), so it might be worth your while to look at a good extended warranty also. I hope this helps.