Even though I've just entered the business by one foot, I'll give you my cents too.
First, get some damn fine knowledge - obvious, I know. Then decide which area of the business you want to get into. I'm biased by noncetonic, so I'm currently working my way towards red teaming. But what I'm currently is doing, is starting on my own. We're four people who decided that it was time to do something about it, if we wanted to do this full-time. We then formed a group/company and started offering our services. I got some nice IRL contacts which has been really valuable in landing our first contracts.
I wish you the best of luck.