That assumes you want to run the country/government like a business. I think that's a fairly large assumption.
The main difference between running a country and a business, is values and also means. Countries value certain qualitative indicators more than a typical business would (quality of life, crime, safety, etc...), and countries have more means to balance the books (things like printing money, ownership of resources, etc...).
Talking about money at small-business scale is more about simplifying the concepts, but to a certain degree, it applies.
Economics is often counter-intuitive - especially at a global scale. People extrapolate their intuitions from household economics to national level and beyond. There's no guarantee that any of our assumptions are still valid when you consider the entire world as one closed system.
There really isn't a problem with government making genuine investments. Needed infrastructure is a great example. They actually do pay even the government back, in the form of increased tax revenue.
The problem is that government often says that something is investment, but it's really just expenses. Bridges to nowhere, and a blizzard of other pork. But government decides where to spend via politics, not rational economic analysis, and so government spending is much less efficient than the label says.
Government should borrow to invest in the country. The problem is getting them not to borrow to throw the money away on political boondoggles.
And what is a more sustainable practice to increase revenues: price gouging, or increasing volume/sales?
Now replace these business terms with economic terms. Cutting costs = austerity. Price gouging = raising taxes.
What you want is more people working, more people paying taxes, but keeping taxes at a low enough rate that people still benefit from working, increasing productivity, and keeping their money in the country. It's a maximization curve...
The main problem with austerity is that often the first thing to get slashed is government labour and infrastructure projects, which drastically cuts the size of the workforce, and immediately reduces the amount of taxes coming in, leading to a tax raise, capital flight, and the downward spiral that all economists warn about.
Just like in business there's a certain rate at which loans make sense and a certain rate where they don't. As long as the cost of the loan is less than the interest you'll receive from your investment on said loan (and inflation helps reduce the cost of the loan), you may as well borrow.
"Austerity" in most cases is just a way for predatory lenders to ensure quicker payment, it's by far the worst economic policy.