"one of the keys is basic maintenance know-how. Anyone can learn to do the basics (oil changes, air filter, spark plugs, brake pads, etc.) with a few hours of learning on YouTube."

I don't think it makes sense to say that is a key, because the basics have to be done equally on newer and older cars and it's easy to find someone to do them for a reasonable price. The issue with an older car is that it is more likely to have non-routine repairs, which tend to both be expensive if done by a professional and hard to assess how much they should cost.