I want to open computer training center on residential purpose Bd

Thank you for reading my question. I am preparing to open my own biz in Kolkata as a foreigner. I have found a good location for computer training center, 1000 sq ft, 2nd floor of total 3 building. The owner explained he can't issue NOC for the commercial purpose when I asked him I need it for establishing my own company to Gov. (If no needed NOC, rent for me is no problem.) So I am very confusing about this. 1. Could you teach me the nature of NOC. Is there any type of NOC, also Is there any fixed format from your GOV? 2. I have read some articles from Internet. Needed cooperative housing society approval, and 20% Max redirected usage for commercial, then maybe State Office confirm of it. But this building is owned by only one person. It looks like there is no society around it. On this case, If the owner can issue NOC for me (if also there is no divided into residential purpose and commercial purpose), Can I use the 2nd floor (In India, 1st floor) as commercial purpose? 3. And under 2 occasion, Can I get the registration of my own company from State Office? I will appreciate with your warm reply for this.