The owner, his/her attitude/house/class is a big part in my opnion,
I don't think the owner will be an issue because when you're buying a NEW car, you need to go to the dealers. I think the things you can do is check the internet for reviews of the car and see what people think of it. Then, if you like what they say about the car, take it for a test drive and if you like it, get it. I would personally check same purposed cars from different brands before deciding because it is a lot of money you're putting into the purchase.
Or if you meant new like newer than you currently have, then i suggest you pay some garage to take a look at the car - suspension, wheels etc. Maybe even an engine checkup. You never know what you get and the sellers might not be telling you the whole truth. Much better to spend a couple of pounds beforehand to find yourself in a situation where you need a lot of money to just get the car running again. Check for any unnecessary leakage and whether the car starts OK with a cold engine. Also the gearbox - try changing gears a bit faster than usual to see if the Synchros make any noise.
EDIT: If the owner does not allow you to take the car to an inspection, walk away.