By mixed land use you mean that commercial and residential activities can be carried out, right? If that is so then yes you may run a property dealing office from there.

All legal commercial activities are allowed in such plots/houses.

Yes you can do the same

1) obtain prior permission of Delhi muncipal corporation for inning property office 

2) The Municipal Corporation of Delhi would now permit property owners to use basements for both professional and commercial purposes. For instance, in posh colonies under categories A and B, residents would have to pay Rs 4,375 per square metre for conversion”

The National Building Code regulations say that a basement can only be used for commercial purposes, or storage, parking, cellar, a dark room or even space where machinery such as air conditioning can be installed legally. However, despite this rule, many may opt to rent out this space for the residential purpose. This is illegal under the law. The fact is that you cannot use this space for your such as a kitchen or a bathroom according to the building bylaws. You can still use it commercially on legal grounds after proper permission of the area municipality is taken, as this is a part of your residence. 

Dear Sir/ Ma'am,

Kindly obtain the prior permission of the Delhi municipal corporation for letting out the property office.
As far as I believe, the Municipal Corporation of Delhi now permits property owners to use basements for both professional and commercial purposes.

Thank You.

- According to the National Building Code regulations, basements can be used for commercial purposes, storage, parking, cellar, dark room or a space where air conditioning machinery can be installed. 

- However, Completion certificate from MCD is not enough for running a commercial activities from basement , it required to take permission from the MCD for running the same.