You say he worked on this for many years. How old is the patent? Could be new or old but it makes a difference as they expire after 17 years. Also do your own

You say he worked on this for many years. How old is the patent? Could be new or old but it makes a difference as they expire after 17 years. Also do your own informal search for prior art to at least understand whether his patent is novel... most aren’t. Patent examiners famously do not do a good job at this determination. Also the patent may well be worth 100m in his dreams but in the real world it is execution of ideas that matters and makes value. Ideas are worth basically zero without execution. But he may take offense if anyone tells him this! Of course patents may be worth slightly more than bare ideas but it really depends on the patent and the prior art. Many patent lawyers will gladly file any patent as long as they are paid, even for a poor quality idea that should be unpatentable or that has prior art, or that offers no protection due to workarounds being available. Good luck.