sorry,i am not getting your question.do you want to create a separate bitcoin wallet just like blockchain wallet,bitpay,bitgo,etc or you want to create wallet in bitcoin wallet sites to initiate your business with it.if you are thinking of creating a separate wallet then you should have understanding of c++ ,web (API stuff)and mainly blockchain. there is no risk as it is decentralised but do not opt for buy and sell option as it require KYC stuff now,it can create problem in future.
Thanks Prashant I want to make wallet like Zebpay and similar what will be the cost for it