There is no same answer to this question, but there are some tips and questions that will help you figure it out.
First of all, think about why you need a balcony? If you have a large plot, you live outside the city and fresh air will constantly circulate in your house, then why spend money and plan to build a balcony. If you live in the city, you have a very small plot of land, there is constantly lack of air from harmful fumes in the house, then yes, most likely you should think about building a balcony.