They are interchangeable but "because" is much more common. "As" is very formal and is not used by most people in everyday speech. I always use "because".

They are somewhat interchangeable. But I would say that one would use BECAUSE at the beginning of a sentence and AS would be part of an ending. Because is more direct while AS is more subtle. Because is a cause and effect. As is more of an explanation. I hope that makes sense.

Lee Wright is right. I would also add, in your example, you wrote "He has much money". A native speaker would never say that (at least not in the USA). "He has A LOT OF money" would be used. And avoid the common spelling error of "alot". It's two words! And "allot" (with two L's) means "to give someone (an amount of something) to use or have"