Hello aspirant,

First of all, it is all depend upon your locality or the place you lived in. Your contact of sources, your talent, your designs and many factor held for the private firm. If you are doing good and have projects in your hand then your salary for one month is around 20k to 40k. If you earn more than this then you are good in this field. As maybe you know that fee charge by architect are really high and all depend on the project. So it comes, if you have large project so you earn more money. 

Basically it doesnt have a specific amount of money you earn in private firm. But according to me, a self estimated gou earn around 25k a month.