As I have noted elsewhere, I have personally known one where I know for certain his family (also not rich, visited their homes for years) was worried about his old car tires' safety for a long drive home, and two others tangentially who I'm somewhat confident were not rich. Another, Bassett, I knew when young, then he made good as a founder/owner in the auto-auction business (where I have a little grunt-level experience). Elder Gay was founder/executive in a private equity firm (quick wikipedia search). The prior careers are available on-line, I'm pretty sure, because there is always some blurb about their prior bios when they are called. Another I knew of in another state who started and ran a locally successful accounting firm. Nelson is widely known to have been a heart surgeon, and it goes on & on.

Edit: I found a page with links to their bios (fairly international, if you read down & click photos), that indicate education & prior careers: https://www.churchofjesuschrist.org/church/leaders .