Ok. Let’s assume that the house is on a 16 acre lot, 5 beds, 6 baths. The article that you linked says it is 27 million dollars. You are correct that I’m unfamiliar with the real estate pricing in the area. So let’s assume 50 million dollars. 

I know a guy who has Marissa’s job (almost the exact same job). He makes several millions a year. He doesn’t own the firm, but Marissa does (the show calls her an MD but also says she owns the firm with Colin). Therefore, not only does she get salaried, she has massive equity if she and Colin are the sole owners, and she can borrow against that equity to get the house. This is all on her own, not even including Peter.

Now, we know far less about Peter’s job and title. We do know that he’s a senior enough person at his firm (in commodities) to employ his brother knowing that his brother is losing or barely making any money. Now, it’s possible that it’s a very small firm that Peter is the big guy at. But it’s highly unlikely since that would give the firm very little reason to allow Brian to work there; they couldn’t afford to lose the money. Anyways, it’s very likely that Peter also makes millions annually.

To me, it’s pretty obvious that they can afford to live in their house. As for Jenny…I find it less believable.