First step to start your manufacturing unit.
Form a company,
Register it in ROC,
Register it under shops and estd.
Based on business type, product and, or service and no of employees as per applicability,
Get the factory license,
Get pollution control board certificate,
If product is food material or eatable ,get FSsi registration.
If Boilers installed, get boiler certification done.
If the factory is in Industrial area, get approvals from industrial development corporation for better amenities, power water light etc.
Further, in operational phase,
You have to ,mandatorily get all statutory licenses and registrations as per labour laws ,GST , Professional taxes etc
During construction phase BOCW registration will be required.
Advise, Start with small, step by step get necessary registrations as required. Get consultation from experts and meet people in business to know more.