First get a domain name then design your website. Then register your Business.
In Parallel , contact Private Travel agencies and Travel companies , get a deal with them -> they will then give you access to their database portals -> This access is a must for designing your website .
For booking RTC tickets you won’t get much margin and they won’t give you commission for the tickets you book like private travels do So best of luck with that.
You will need good Business contacts ,communication skills, patience, Money for Initial Investment and time to pull this off.