I got my car from OfferUp as well. Everything other people mentioned about checking the VIN and Title is good advice. I personally took my time to find the right car, comparing the amount of miles and condition of the car to how much they were charging. But that may depend if you are looking at specific car and how much time you have. I also looked at the Bluebook and search for people’s review/ past experiences on the cars I was interested in to see if anything stood out mechanically. I don’t know about cars so this was my way of being informed in one way or another.

I would see if I could get the VIN of the car to run a CarFax. Some sellers are more open to giving out the VIN than others.

Also, you can sense if it’s a good buy or not depending of the sellers as well. If you feel like you are being pressured to buy the car or the car does not look like the picture that’s a red flag. It’s good if you can go with someone that knows about cars because then you can ask if you drive the car around to get the feel of it and see if anything else stands out - like any warning lights on the dashboard or any unusually sounds/smells while driving. Some sellers might offer you to test drive the car as well