Being a coach in our times is not among the jobs I would decline because of the pressure and the danger to lose my job today or tomorrow. If they sign their contracts and get sacked, life goes on on the Bahamas or Maldives or Mallorca or wherever their holiday mansions are. They don't care. Bayer Leverkusen is backed by pharmaceutical giant Bayer and money has never been a problem for them, especially now that they sold Wirtz and Frimpong. I think ten Hag will get the money he wants, at least for most players. The finances shouldn't be the reason he can't be successful.
Manchester United has also shown that it knows how to secure funding for transfers and how to get the players it needs. If I'm not mistaken, during the few seasons that Ten Hag has been the manager of Manchester United, he has signed more than 11 players. In fact, you could say that he completely rebuilt the entire squad through transfers. And I agree with you that Bayern is a club that has never had problems with money, so if necessary, Ten Hag will get the funding and the players he believes he needs.
The other thing is that he hasn't acquired the best players in terms of chemistry. Either way, only the course of the season will tell what happens in the end, I don't think they will be able to acquire better players, if at all. Moreover I think Leverkusen is not a team whose management will tolerate constant failures, they will hire a new coach if they do. For now MU is a dark stain on the coach's reputation, after a successful stint at Ajax