For interior design, it is not essential, but there is in an increasing interest in individuals to have formal education. Some programs are 4 year programs or 2 year programs. I found this site that might help for program options: https://www.niche.com/colleges/search/best-colleges-with-interior-design/s/new-york/
While finishing your schooling either high school or college, some people work as an intern at a local interior design company, even for free. A lot of companies might not be able to hire you, but if you can find a way, there are a lot of people need help and this could provide great experience to put on a college resume as well as get some insight into what a typical day would be. If you are a hard worker, sometimes these positions turn into a small position or the company can be a reference for another company as well. Networking is really helpful in getting your resume to the top of the list for hiring companies.
To be a real estate agent, doesn't take a formal education, but there is a pre-licensing course that will help pass the licensing exam.