Hi Sweta,
While it is relatively risky to start a practice after 15 years in industry, over a period of time, it will definitely going to be rewarding. Initially you will have to spend time in building your individual identity (as a Subject Matter Expert) and leverage technology (Linkedin, Twitter, Practice Management Softwares etc).
Please be aware that it'll take time (years) to match the cash flow from job, however once you have built your firm, it can grow exponentially over a period of time.
Starting a practice along with job is not recommended, it creates conflict of interest and your job will keep you in your comfort zone to not take more risk.
All the best!