Welcome - if you do some searches on buying a car there is more than a weeks worth of reading on this site. Use the search box to search anything and keep searching different words.
Based on what I have seen first hand - find a car that you can physically touch and drive. Take no excuses for not being able to drive on the day you see it and look for rust in all of the locations. Go through the archives for areas of rust, there is a schematic of a car showing rust prone areas and get to know those areas first hand. I got a 1:18 sized model and put stickers all over it for things to look for when I got my car and yes - I found evidence of rust in all but one of the rust prone areas.
Take your time - these cars are not rare but they don't seem to come up too often in certain areas.
Hit the car shows and talk to the owners.
Good luck
