Do you need a mentor, or not for when you're making music? I definitely think it's a massive plus. Most of the things that I say, mainly, have come from mentors that I've worked with.

In my early days, I didn't have YouTube etc, I only had guys that I worked around, who had been in the business, always mastering, cutting vinyl since the 60s. I always followed them, listened to what they had to say in the studio, checked their settings out, had them telling me what I should be doing, what I shouldn't be doing, how to deal with people, watching them work and learning every day, leaning on them when I got stuck. It's been a massive help to me, to just be around these guys and have certain ones that I've just gone, "Okay, I really like this guy, he knows what he's talking about, I'm gonna follow his style and listen to what he's got to say etc.

I was very limited in the mentors with teaching me and helping me and giving me advice and things, and that was lucky because these days on YouTube etc, there are too many people to watch, some with too much false information, It's very easy to go down a lot of cul-de-sacs. However, if you are following the right people, and you're listening to the right advice, then you're going to go in the right direction.
It's very easy to sort of get drawn into somebody's personality, because they're good at talking to the camera, but they might not actually have any experience, so I would do some detailed research on the people that you're following, and the people that you like, just to make sure they do know what they're talking about, they've got the experience and the knowledge, so you can know what they're saying is the truth, and not just made up from what they've actually heard from somebody else making up before then. Then it's just a load of made up stuff and no one's actually done any real work with real clients in the real world!
It's so easy just to throw videos up, even if you don't know anything these days. 
So, Watch who you follow, it's super important, don't just follow the first person. Watch who you're following online, make sure they know what they're talking about, stick with just a few.

You need to be getting on with stuff, you need to just have one style, from one person, and then you can then develop yourself through that, I'm not exactly the same as the mentors that I had. I listen in a different way, I've got different experiences in my life, which makes me craft the sound in my own unique way.

Find follow and use experienced online mentors to take snippets of good advice for you to be able to craft your unique style too.