Is it a bad idea to dive into business without working for someone first?

Im 16 and i want to be a businessman and start my own business like right after uni or during uni but im being told by people older than me that "you need to work for someone first" or " you need to work for like 3 years minimum then start you business" but i find that complete bs cause i dont wanna drag the opportunity to feel comfortable
so,is it really a good idea to start right away or do i need work experience