Ben Affleck, Jennifer Garner -- No Prenup, No Money Problems

Ben Affleck and Jennifer Garner did not build a financial wall between them before getting married, because we've learned there is no prenup ... and get this, he's not that much richer than her.

Multiple informed sources tell TMZ, Ben and Jen's business managers are busy figuring out how to divide what we are told is a fortune. We're told they both have accumulated many millions. Jen made a "massive amount of money" off of "Alias," which went into syndication, as well as a string of movies, including "13 Going on 30" and "Elektra."

Ben has made a ton of money, but a number of his projects were independent films where the cash wasn't as plentiful.

Short story ... they're both rich, but it's not like she needs his money.

It's unlikely she'll get spousal support because of her wealth, but she doesn't need it. The trick is dividing the community property, which we're told is going smoothly so far.

As for the "10 year rule" -- meaning a judge would give her more spousal support due to the length of the marriage -- we're told 2 things: A) their decision had nothing to do with it B) she's loaded and doesn't need support.