Provided that he/she submitted all his/her documents.
It depends upon the broker. Some brokers promise 4 hours to 1 day and with few others it may even take 7 working days provided the documents reached the broker and are well established.
Usually for demat it takes much longer usually 2 weeks at least but for futures or commodity MCX market its 2 days or even less. You can just contact your broker and ask
Once you have submitted your application for an opening demat account account, you will have to wait for its processing. It usually takes a week or two for the completion of the verification process.After submitting your application, the DP carries out verification of the details provided on the Account Opening form. On completion of the verification, your application is processed and a welcome kit is dispatched. The welcome kit contains your user ID and password. You can then log into your account using these details and begin trading online. It is advisable to change your password for security reasons.
Zerodha got my Demat account opened in about 3 days. I had gone to their office to submit all the documents which made it easier.
Also, Demat account is needed only to take delivery of equity stocks. The trading account is opened within 24 hours by them, so you can start trading in F&O in 24 hours of submitting documents.
The digitalization has added efficiency in the system and the time for opening dmat accounts or other trading accounts have been reduced to mere few hours and with proper documentation the things tend to turn around at a much faster rate. The online players like tradebulls have further simplified the access process by there user friendly interfaces and have also positioned themselves as the financial adviser of users who are using there services.