I got stuck so used the walkthrough, and it appears I may have found a bug? (unless I'm missing something even when watching the walkthrough).
There's a lever that keeps springing back up (rather then staying in the down position) every time I click it but in the walkthrough it's clicked once and it stays down...
For those of you experiencing the "offline cash" bug: I'm fairly positive the problem comes from not having the game window in focus when the game loads (e.g. you open the game then look at another website while it loads up).
Therefore, to hopefully reduce the chances of it happening to you, be sure to keep the window in focus until the game has loaded and it has worked out how much cash to give you.
Obviously I can't 100% guarantee that this will solve your problem but it appears at least for me that this is what is causing it.