Merhaba.

Would you place "bir" in this setence?

My son is a writer - Oğlum (?) yazar.

 I have been told that using the ´bir´ is unnecessary, unless you add adjectives.

Oğlum çok iyi bir yazar (My son is a very good writer)

Oğlum ünlü bir yazar (My son is a famous writer)

Oğlum yazar(dır). My son is a writer

You can say: "Oğlum bir yazar."
Also you can say: "Oğlum, yazar."

No difference between "Oğlum bir doktor." and "Oğlum doktor."

But "Oğlum bir yazar." is more clear than "Oğlum yazar." because of the verb "yaz(-mak)"

yazar: (as a profession) writer

also
yazar: he/she writes, simple present tense.

If you use "...bir yazar", it definetly means a writer, an author. No confusion.

@ikicihan

Yes, honestly that´s why I asked for this example

I knew it´s quite ambiguous and I wanted to know if Turks would rather do something to avoid the confusion, like putting "bir" before the noun. And now I know you do