What does a dream about seeing a rich man that came and drank from your house mean?

This dreams suggests feeling of being taken advantage of by those who have means and power. The rich man represents those who have access to resources. Instead of drawing (water) from their own plentiful resources, the dreamer feels that others are taking away the little that belongs to the dreamer. It is important to note that the dream represents the dreamer's feelings about exploitation. It is not evidence that the exploitation is real. See the attached link for further examples and discussions of dreams.

A different opinion:

Absolutely nothing. You had a dream. It is a function of the subconscious mind.

Dreams are a function of the subconscious.

The symbols in those dreams have different meanings to different social groups. It therefore depends on the group to which you belong what those symbols mean.

For someone that has no knowledge of the group to which a person who dreams belongs and to claim to be able to interpret those symbols is nonsense.

Dreams mostly mean nothing and are a function of things that are poorly understood. We know little of the conscious mind let alone the subconscious one. Those people that claim to be able to interpret the subconscious are charlatans, playing upon the insecurities of people. Either for financial gain or kudos.

There are as many different interpretations as there are people that claim to interpret them. Palm reading phrenology, Astrology, the belief in vampires etc., all belong in the same bag..