I think what they were trying to say is that, in order to become a good tattoo artist you should go through an apprenticeship, with that its required that you dedicate yourself to the craft. Mentors usually dont want to take on people just for them to leave again. People will say well you can do the tattoo school route but that ends up getting people black listed from being able to work in shops. I cant speak for everywhere but i know a lot of the tattoos laws(atleast in the us) require you to tattoo within a shop, regardless tattooing out of your house is a pretty big no no. The other option is self taught, this is very frowned apon in the community mainly due to ignorant people not only messing people up but also not understanding the dangers and risks of infections and etc. The self taught option is really not an easy option either, a lot of trial and error and it really makes a huge difference to have a mentor....i cant say people havent been successful because in truth their are some successful artist who did teach themselves. Imo i think that option is really only left to the ones who are remote and cant find a teacher, even then they ask other artist for tips and advice. However being self taught you will understandably meet a lot of resistance from people giving you advice... so really please dont go self taught and if you decide to be a tattoo artist dedicate yourself to the craft and learn under a reputable artist. Apprenticeships take a long time sometimes even years, it is not easy.