Being rich doesn't mean you are happy.
Being a successful person in life is a big challenge.
Being a doctor doesn't mean you are smart.
The sense of "being" at the start of a sentence depends on its context.
In all the sentences being has been used as a gerund. Being rich, being a doctor, and being a successful person are gerund clauses that are subjects of the sentences.
These sentences imply as follows:
If/when you are rich, it doesn't mean you are happy.
If/when you are a doctor, it doesn't mean you are smart.
It is a big challenge to be a successful person in life.
You can also use to-infinitive instead of being, but the use of the to-infinitive isn't so common.
Besides, in the construct of some sentences, being is also used to express a reason or cause as an alternative to because, since, or as. For example:
Being the youngest, Sara is her father's favourite.