If the business that is inherited is very large and the money circulating in it is also very large, then yes, the advice is clear, however, he must have good management of the company's money, make sure that any allocation of money is used for targeted things, and make sure to be careful and alert whenever you place your trust in people, including business partners, because usually money is a priority for everyone and sometimes business failure is usually always triggered by mistakes in managing money or carelessness in placing trust in someone (business partners) who ultimately put their trust in people who have evil intentions.
18 years old is an age that tends to still be childish or meaning that it has not really reached the mindset of mature maturity and clearly this can cause problems when making decisions, what is worried is that it is very likely that he will make careless decisions, and according to I'm too young to manage such a big business and it's too risky, but if for example they are someone who really wants to learn then maybe over time they can develop knowledge, skills and management which can become experience to become better in managing the company or business.
If a young inheritor is willing to learn and actively seeks knowledge and guidance, they can grow into the role over time, gaining the skills and experience needed to manage the business
Yes because on the other hand it is good to learn something from an early age or from a relatively young age where you have a lot of time to learn something freely in order to become someone who has a lot of knowledge, insight and also knowledge, but yes maybe it also depends again on the intention and sincerity of the person in his learning period. But if for example the scenario as told by the OP where his parents inherited the big business when his son was still at a relatively very young age then I think this is not easy to live with especially if for example he doesn't know much about how to manage and organize the business properly, although on the other hand he can learn but I think the time is very short to learn everything because the business is already running which may be no other way but he has to really spend more time learning everything.