<UPDATE: After plummeting overnight on the Trump election news, U.S. stock markets rallied and finished up for the day.

In what can only be described as a head-spinning upset, Donald Trump--the billionaire businessman from New York--will officially be America's 45th president.

At 2:31 a.m. today, the Associated Press tweeted that Trump had won the presidency. According to multiple media reports, Democratic nominee Hillary Clinton called to concede the election shortly thereafter.

"She congratulated us--it's about us," Trump said, gesturing to the jubilant crowd who had gathered at his victory celebration. "I pledge to be president for every citizen of our land, and this is very important to me."

What does his unexpected ascension to the presidency mean for the business community?

According to a CBS news exit poll analysis, Trump is seen as a better steward of the economy than his opponent. Looks like he'll get the opportunity to show off his skills.

Among other things, Trump's economic plan involves cutting taxes, eliminating regulations, and overhauling trade deals. Doing so, he says, could help grow the economy at a 4 percent clip. (Currently, the U.S. GDP is growing at an annual rate of around 2 percent.)

Robert Litan is skeptical. The adjunct senior fellow at the Council on Foreign Relations, a nonpartisan think tank in New York City, suggests looking at the stock market as a guidepost. In after-hours trading when a Trump victory became apparent, the Dow, Nasdaq, and the S&P were all down roughly 4 percent. And while you might think smaller and privately held companies are sheltered from these fluctuations, Litan points out that there's a trickle-down effect. "If the fall in the stock market continues, that suggests a higher risk of recession, which can't be good for small businesses and startups."

Plus, it's not so easy to cut taxes. While Congress is in the hands of a Republican majority, getting Democrats to go along with cutting taxes for the wealthiest Americans--as is Trump's plan--will be a tough sell; while the Republicans control the Senate, the Democratic minority could filibuster bills they don't like.

Under Trump's tax proposal, top earners--taking in more than $699,000 a year--would see average annual tax reductions of about $215,000, according to an analysis by the non-partisan Tax Policy Center.

Companies could see an even bigger payoff. He'd reduce the corporate tax rate to 15 percent, from where it stands now at up to 35 percent. Many small businesses operate as limited liability corporations, sole proprietorships, and S corporations, which are all pass-through entities. It's not clear which pass-through entities would be eligible for the lower rate.

But since the Republicans control both houses in Congress, he'll have a lot more free rein. That means the Affordable Care Act--the landmark health care law that passed in 2012 and established, among other things, health-insurance exchanges and required all Americans to have coverage--will surely wind up in his crosshairs. In speeches, he's said repeatedly that it would be his first order of business. Among other things, he's cited rising insurance premiums as his reason. In some states, the cost of coverage is expected to rise by as much as 25 percent, according to a report from the health care researcher Kaiser Family Foundation.

Further, he has also vowed to remove an estimated 11 million immigrants living in the U.S. illegally, as well as cancel visas to countries that refuse to take them back. He has also proposed an outright ban on Muslims coming into the country, as well as building a wall on the border of Mexico. (The logistics of accomplishing everything listed in this paragraph, to put this in the gentlest possible terms, are extremely daunting.)

For businesses, specifically, Trump has proposed closing the H-1B visa program, which is the federal program that allows for as many as 65,000 skilled immigrants to work in the U.S. each year--and which huge U.S. companies like Facebook and Google use regularly to engage foreign skilled workers. Trump has said that he would require companies to hire American workers first for every visa and immigration program.

Some observers caution that, even with a Congress fully held by Republicans, these proposals might be tough to greenlight. "The electoral advantages of anti-immigrant politics will only shrink over time, suggesting that Republicans should at some point-- perhaps before the next presidential election--begin to embrace comprehensive immigration reform," says Mark Price, a labor economist at the Keystone Research Center, a nonpartisan economic policy think tank in Harrisburg, Pennsylvania. Regardless of who won this past election, the party might attempt to shake off its current image--particularly as demographics continue to shift.

What is popular among Americans these days is curbing global trade. That's something you can almost guarantee in a Trump White House, say observers. Not only has he discussed withdrawing from the Trans-Pacific Partnership, a trade pact favored by Obama that would lead to improved business ties between the U.S. and 12 Pacific Rim nations, he's expected to attempt to renegotiate the North American Free Trade Agreement, or NAFTA.

All of this is to say that we're about to enter a period of uncertainty, and that's not great for business, says Price. And while largely people knew what to expect with a Clinton presidency, with Trump, a political outsider, it's hard to tell.

As such, "the next 12 months are hard to predict," says Price. "Beyond those larger themes, businesses will, like the rest of us, need a few months to get a better sense of the direction of the Trump presidency."