A (financial) difficulty option

You're looking for ways to make the game interesting. Here's a HUGE one. Offer optional financial difficulty setting (more than one level) because it suddenly becomes more interesting if it's actually a challenge to make money. 

It's easy to implement: The difficulty setting would decrease the % of money you gain any time you gain money from anything in the game.  Default = 100%.

So for example: 75% would mean you only get 75% of your salary (losing 25%) and you only get 75% of any other amount of money you would have just received.

Not sure how low that % would go before the game would become too difficult, but definitely offer different levels, if not a "enter your %.  100% = default, 10% = the most difficult" 

As it stands now you're given so much money for everything you just end up with far more money than you can ever spend and it robs the player of that aspect of gameplay, making money POINTLESS.

But if now there's an option where at early stages of a career or other hobbies it's a struggle to pay rent and get food and items, that adds a ton of gameplay to the game.

Food for thought.