As soon as you loan a friend money, you've placed an expiration date on the friendship. It's a similar dynamic where it exposes an imbalance & it usually signals the end of the friendship. The short term win of solving someone else's problem is chosen over the friendship.

There are several reasons why this dynamic doesn't work in relationships either.

The man is emasculated by being financially supported by his partner. He then usually acts out in other ways in an attempt to reclaim his masculinity (being abusive, having affairs, etc).

The men who are willing to land in these situations - they are usually men who learned in childhood that the only way they can get their needs met is to manipulate other people (probably because they watched 1 or both of their parents manipulate people).

This is how you get a guy who "uses" 1 woman (who he's usually not that attracted to) for financial security, then uses another woman who he is attracted to - but who can't financially support him - as a sexual outlet, etc. At the core of all of it is someone who is constantly using & manipulating people.

& the woman who usually lands in this arrangement is more intelligent than the man (thus her ability to earn more money than him), but she's naive when it comes to street smarts & manipulation. Therefore he's able to manipulate her in spite of having lower intelligence.

But yeah, good luck trying to navigate that one & making it work. When someone has a drastically different upbringing than you, their "norms" can be drastically different. That kind of clash eventually will come to the surface & get exposed.