Donald Trump means business – but what does that mean?

As he suggests Fed head Janet Yellen could be for the chop and reports reveal America's GDP could shrink...

So against all the odds, after all the snorts and guffaws, Donald John Trump has seemingly secured his position as the Republican candidate for presidency of the United States – unless the Republican National Committee pull off something unprecedented – and realistically only Hillary stands between him and the White House.

He's made much of his billionaire status on his "self-funded" campaign thus far, but there the feeling that Trump is more excellent self-promoter than shrewd, intellectual businessman still remains.

Indeed, reports late last year showed that if he had simply retired three decades ago and invested the fortune he built from the tidy inheritance he received from his New York real estate developer father, he'd be a lot better off financially.

So if the seemingly insane happened and President Trump was inaugurated next January, what would that mean for the US economy?

Well, the Apprentice host has already sign-posted some of his drastic moves, which could soon mean a dramatic shake-up for the Federal Reserve.

Talking to CNBC this week, Trump admitted that he would "most likely" replace Federal Reserve Chairwoman Janet Yellen if he comes to power.

He said:

"She is not a Republican. When her time is up, I would most likely replace her because of the fact that I think it would be appropriate".

When it comes to the Fed, it is not always the case that presidents act along party lines. Bill Clinton twice crossed the aisle to renominate Alan Greenspan, a Republican, while current US President Barack Obama renominated the Republican chair Ben Bernanke in 2009. Yellen's current tenure ends in February 2018.

Meanwhile, a study released by American Action Forum this week forecasts that Trump's vow to deport all of the country's undocumented immigrants could shrink the US economy by 2%.

According to government statistics, approximately 6.8 million of the more than 11m illegal immigrants in the US are in employment.

Removing them could cost a massive slump of between $381.5 billion to $623.2 bn in private sector output.

The move could also leave potentially millions of US jobs unfilled because citizens are unwilling to do the work in areas such as farming, construction and hospitality.

The forum's president Douglas Holtz-Eakin (who was also the chief economic adviser for John McCain's 2008 presidential campaign) said:

"The things Donald Trump has said are utterly unworkable".

Trump disputed the findings on CNBC, saying:

"I saw that report and they don't even have it right. We certainly don't want to shrink our economy".

When it comes to the ever-present debt problem the US faces, Trump has some easy solutions, suggesting low interest rates are good and if they should rise, the nation could "renegotiate longer-term debt".

He said:

"I could see renegotiations where we borrow at long term at very low rates.

"I have borrowed knowing you can pay back with discounts.

"I was swashbuckling, and it went well for me".

Trump continued:

"We have to be very, very careful, and I am the king of debt, I do love debt. I love debt. I love playing with it. Of course, now you are talking about, you know, you’re talking about something that’s very fragile".

He also discussed his much talked-about tax plan with CNBC...

"When you put out a tax plan, you are going to start negotiating.

"You’re not going to say, 'Okay, this is our tax plan, lots of love folks.' There’s going to be a negotiation back and forth".

Trump's plan will reportedly reduce US government revenues by $9.5 trillion over a decade.