How to get an online Wallet Website? How much will it cost? And how long will it take to be built?

Brother a project like this one cannot be answere in a single paragraph. You should know that you will of course first need government licensing & clearances before you can even think of creating such a website. You will need to consult a developer with all your features pre-decided. You will also need proper consultation throughout the process. And you are talking about something like PayTM. Be prepared to get quotations in crores. You should contact an eCommerce Consultation Company if you have investors for such a huge budget.
But here’s the catch! Lets say that you just need an eCommerce Website with just in store credit system (which will not be in Rupees but credits) then that would cost you way less. You can get a simple eCommerce Website built in about Rs30000 as on March 2017. Let us know if you have any further queries about that.