How and what should be done to prepare the wood to be repainted?

1. scrape any loose paint.
2. brush or roll a good primer on it (I recommend Binz or Kilz).
3. paint it with a good exterior paint.

That should leave your neighbor in good shape for the next 5-10 years.

Scrap and remove all loose paint. Paint does not stick to treated wood very well, especially in direct sunlight. If you got 9 years out of the last paint job you are doing quite well.