How to sell companies personal data

I have been wondering how these startups make money. Pretty sure they sell data. I just want to know if there is a legal framework which allows them to do so? I am asking specifically from Indian market's point of view. Can a company's source of revenue be from selling customer data (legally)? What if customer of an app XYZ voluntarily agrees for their data to be sold in return for some rewards or maybe even without rewards. Please share your views and facts about the same. If someone has any idea, can they shed some light upon a rough price range in which the data is sold. Like I want an idea what's the quantum of cost of that data. Mis it in 100s per user or thousands or what exactly. Just a rough idea.

Asking for self 😢

I want to know what does a fintech or a money management app does with all the data that they have. Do they sell it to other fintechs directly so they can sell products to customers or do they also sell it to brands for customer insights

Have you ever experienced a situation where you applied for a job on a company that is a hiring platform, but instead of receiving a response regarding that job, you start receiving job openings from the platform itself? It appears that they create a fictitious role and utilize it to send job notifications from companies hiring through their platform.

Hi all, I am thinking of creating a job board system which 1. scrapes the job data from the company's official pages 2. do not encourage third-party talent acquisition firms to spam with duplicate posts How do I make money? 1. Selling home page slots to the companies that promotes high visibility Do you guys think this will work?

Hi, I resigned from my job to do startup. I have no good Idea now. Anyone have any idea that you really believe will work but you don't have time , energy or motivation to work on. Can you share it if I also believe in that idea i will work on that. If the idea do well or I get funding. You can join me as Co-founder and we will make it big.