Salary Adequate Family Expenses and Cost of Living (Brussels)

Dear All,
I am considering accepting a job offer in Brussels in the architectural field and is now in the process of discussing the offer in detail (salary etc).
My question is what is the range of salary would be considered adequate for a family of three, myself, my wife and our son (2 years old) to be living in Brussels.
I am also considering working here on my own first and have the family join me at a later date.
Advices please?

Regards,
Nazmi Anuar