I went from journalism to PR/Advertisting. I'm a journalist. Nothing goes as planned. As long as you have a degree, you can pretty much do whatever you want.
Yes, you can hire a physicist to help an engineer or MBA to do really hard math equations. I equate that with actuarial work. You can hire a lawyer to be a real estate agent or to do your taxes, but most lawyers don't get hired out of school to sell houses or become accountants. Business and engineering are very broad disciplines. Physics and Math are very narrow disciplines, narrower than biology, chemistry, and many others. Heck, the only narrower science major I can think of is Astronomy. It should only be pursued if you're both dedicated, passionate, and talented in the subject.
I was a Journalism major my freshman year. I was an English Education major my sophomore year. I was an IT major my junior year. I was an IT & HR major my senior year, and my 9th semester in my 5th year. Like someone already said, if you took your cores early like you were probably advised to do, then you should be able to just load up with one more class per semester than you usually take, and you can finish on time or maybe with 1 extra semester tacked on.
I didn't pick a major until junior year, and I finished in four years. Now I'm a Business Analyst or something like that. STOP HATING ON POLISCI degrees!!!
I think you'll be at the bottom rung right out of college regardless of what major you get. The majors where you'll make money require alot of aptitude, and for things you might not necessarily be interested in. Find out if your parents will support you for a while right out of college, then stick with (or follow) your interests, find and start reading related trade publications, and do your damnedest to get internships in the field (before or after college).
I wouldnt take the risk these days. If you major in physics, be prepared to go all the way for a PhD or masters in something else.
Would getting a full-time job immediately after graduating with just a BS in Physics be considered useless?