So, it's up to the individual to have enough sense not to go into this business without proper training. Unfortunately, that is why my site and the work I do is necessary - because too many people do not care about that and put their customers at risk. And there are too many companies out there selling tattoo equipment to anyone with money, which only perpetuates the problem.
If your nephew really wants to make it in this business, he has to be trained. That is usually done through an apprenticeship. If he has a friend in the business, maybe his friend will (or is already) training him. I can't imagine that his friend, who owns a shop and will no doubt care about his reputation, would allow your nephew to just start tattooing clients without any experience. If your nephew is serving an actual apprenticeship with his friend, and he simply needs starter equipment to begin practicing (apprentices usually practice on pig skin, fruit, etc.), but you should talk to him about exactly what he is needing and why. If it's because he wants to start tattooing people from home, that is very dangerous and also very disrespectful to his friend.
Does your nephew have artistic skill? Is he the kind of guy that's always sitting around drawing or painting? If that's the case, he may be a very good candidate to be a successful tattoo artist. However, if he thinks he wants to do this because he thinks it's cool, glamorous, or that he can rake in tons of money - he's setting himself up for disappointment. A few artists make big money in this business, and the rest of them are struggling day to day just like anyone else.
Since his mother just died and I'm sure he's hurting, it's probably a really good idea that he immerse himself in something expressive and artistic, as long as he does it properly. If he has artistic skill, he deserves a chance. Just make sure he's doing this the right way. I have a couple of articles you may want to share with him: What Makes a Good Tattoo Artist. How to Become a Tattoo Artist. How to get an Apprenticeship.