Dealing with money in Judaism ultimately reaches expression as Bitachon. Bitachon is absolute rock-solid trust in God. This Bitachon is focused on the reality that: Everything you have is from God, and God gave you exactly what you are meant to have -- there is no way to earn a single penny more (or less) than what God intends for you.
I'm no economist, but it seems to me there are two central aspects to how one manages their money: (1) How much we borrow and (2) how much we spend.
One would think that you are allowed to borrow a reasonably large sum of money to invest in a new business venture, and doing so would show your Emunah (faith) in HaShem. You have faith in God that your venture will be successful, and so you can borrow more than you could afford to pay back, and that proves your faith!
Wrong.
One would also think that only a fool would spend every bit of cash that he has at his disposal and if he were to do so, God would laugh at him.
Wrong again.
The reality is this: Whatever HaShem has given to you is what He wanted you to have.
If you hoard it, then you are saying you don't trust that He will continue to provide for you.
If you waste it, you are really being foolish because you think you don't need it, more than that you are acting like an ingrate.
But, if you spend it where it is needed, and use it to serve Him through mitzwoth, Shabbath, Tzedakka and the like. Then, if you have true bitachon, you will sleep soundly when you've depleted everything you've got.
Conversely if you borrow beyond what you can afford to pay back, you are saying that God didn't provide what you needed.
If you want to start a business, get a wealthy partner to invest his money. If you can't convince him the idea is viable enough to risk his hard-earned money on, perhaps it isn't all that viable to begin with.
As long as you borrow no more than what HaShem has given you, you can rest assured that you are in the clear. This is why a mortgage is okay, whereas a cash loan with no collateral might be a problem, if your possessions are worth less than the amount you are borrowing.
Basically it's better to spend your last penny than go into debt.
Do I live like this? Not yet. It's a tall order, but its the essence of true Bitachon.
It becomes immediately apparent in this light that the classic model we're used to, of borrowing against future earnings is the worst mistake we could make.
May HaShem help us all to achieve a healthy and holy lifestyle, so that we can honestly proclaim, "In God we trust."
