At least 10 fights of either imo. I used to think your record was everything, but I'm in the camp now its your total experience in the career. I've seen guys amass a 12 fight record in a short period of time (some of which are tournament wins which racks up alot if you do indeed win them all), and they're basically an inflated fighter on experience for their skillset, compared to someone who took it normal and took 3 fights a year (shows). A person who's 4-1, and goes pro the following week, is too inexp'd imo. There's so much they still don't know in terms of skill, and plus how the entire industry works, which itself is another entire beast.
There's two sides to coaching. You have the skillset part for the sport, and the knowledge of the game part. Both are needed imo, esp having gone through a coach that was inexperienced in the latter, it fell back on me bad. I've seen it happen to other friends in the community as well, and its not a pretty sight; Especially if your fighter is the one who has NOTHING: no education, no blue collar skill, shit job, possibly a record which makes stable work hard, just puts their hopes and dreams into the sport hoping for that lottery ticket, and using them as your lab rat to learn along the way so you won't make the same mistake 2-3 years later when a hot shot 18 year old shows up at your gym door, who you see as a golden goose. Yeah, don't do that. This type of coaching happens when people lack exp in both sides, and take up gym ownership too early.
Knowledge of the game part would be knowing the connections to get decent fights and even cross-training with sister gyms locally or overseas, able to make sure and to see setups for your fighters from a mile away, and the heart to not cripple your fighter's career by playing it too safe or greedy (have an ex-teammate who's going through that now, should've done pro YEARS ago, but he was told he was too in-exp'd for pro, and now he's 28 with a 2-1 record, while we know of 20 year old killers with even more exp. stepping up the ladder).
I've done some coaching on my end just due to circumstances (teammate's coach was fucking off, and my teammate being a good friend of mine we just trained, and it just ended up being a coaching student arrangement without me realizing it until the 3rd week in). Imo, I still have alot to learn so I wouldn't go around advertising myself as a coach or even open a gym. I have a friend who did that, but he basically opened a fitness gym that caters to business people, working moms who want to get fit again, etc. with the occasional fighter (seems to be 1 fighter per 3 years, and in novice events). Even then, I still wouldn't. I've always been the person that I feel I need experience and actual paperwork to feel legit. I can't in my goodwill open a gym which includes nutrition training where I have no official background in it. But that's just me, others don't appear to have that block and just open gyms for the sake of it.