What is the scope for building a site that is similar to Stack Overflow?

You can build the website like stack overflow even better than to this. To develop a product/website is not a big deal however marketing of the products plays an important roles.

There is so many apps, websites available in the marketing those are awesome in terms of design and functionality however these are not popular like others because they have lack of branding and marketing.

Therefore, always plan for any product marketing and branding as well as invest a big budget on this.