Doing business and buying commercial property while on VISA D

Hi fellows,
Please help me regarding issue mentioned below. Thanks for your time in advance.
I started my PhD as researcher on VISA D with VISA remarks BNL 2, B 13 but then resigned after two month. My VISA was issued for one year and is still valid with Multiple entries so I can still go to Belgium any time till the VISA ends.
Now I want to buy a shop and do business in Belgium. Please guide me that is it allowed under my VISA type (D VISA) or not?
Once again, thanks for your time

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