The person's a serial killer you have some backup that's probably the main one just saying you don't need to be scared though but maybe you should just a little so now on to the first actual step of when you get there to look at the bike fill the engine and see if it's warm if it is warm the seller has probably started it up before you got foam air filter oil and got everything warmed up which means that the bike probably has issues and is hard to start so they warmed it up so that it wouldn't be when you got there next just check over the obvious things such as seat cover plastics tires and just the looks of the engine obviously there's always going to be some scratches and dings here and there but if the plastics are completely rotted the seat cover is torn and rotted away the tires are completely evolved the engine is rusty everywhere.
Air Filter Maintenance Done Right!
It's got oil leaks then that's obviously not good unless that's what you're paying for step three start to check over the chassis sit on the bike with your hands on the bars looking at the front fender and the front wheel and make sure that the bars are aligned and they aren't twisted or bent next you can check the subframe by simply just standing from the rear of the bike and seeing if the fender lines up with the rear wheel if it is straight then you're good to go if it is twisted or shifted off to the side then that means you have a bent subframe then check the seals of the fork and the shock if you compress the fork or the shock and it leaves a oil residue or a little ring of oil that means that the fork seals.

Clean & Oil a Foam Air Filter on Motorcycle
Are leaking and will need to be rebuilt next check the wheels you can make your way around the wheel with your hand pinching the spokes together to make sure that all the spokes are tight they're all there and none of them are cracked then you can spin the wheel to see if it isn't true or if it's bent or out of true then it is good to check the bearings you can check the linkage bearings to see if they are worn out by having the bike on a stand and lifting on the rear wheel if you feel some slack when you lift up that means that the bearings are worn out and depending on how bad it is they may need to be replaced dirt bike air filter now same thing with the wheel bearings you can shake the wheel side to side and if there is side to side slack in the wheel that means that the wheel bearings are worn as well and may need to be replaced and then the last bearing that is good to check is the steering head bearing now you can do this by having the bike on the ground pressing the front brake so that it won't roll forward and rocking it back and forth if you can feel slack right there in the head tube then that means that those bearings could be worn as well then you can check the brakes you can check to see if the rotor is worn out by looking for lines which as you can see my bike does have lines on it but sometimes that's okay so next you can run your finger up and down it.