Are the college admission rules different when you work in a professional field for 20 years without a degree before you apply?

Answer

If you're asking if colleges and universities tend to treat adult students with lots of life experience and maturity any differently than wet-behind-the-ears, fresh-out-of-high-school kids, then the answer is "probably, yes." Such things as SAT scores and that sort of thing are often not required for older adult learners. Your high school transcript -- 20 or more years old though it may be -- will probably still be required, however. If you have previously-earned credit from a regionally-accredited college or university, even if it's 20 or more years old, that is usually considered prima facia evidence that you have a high-school diplma and you probabaly won't be asked for one.

But, if you're asking if the college will give you credit for your life experience in the field, then that's a different question.

Generally, if you've been, for example, an accountant for 20 years, it's a good bet that you pretty much already know many credit hours worth of accounting classes. If you really and truly believe you can effectively "test out" of said classes by virtue of your 20 years of experience, then the univerisity may very well let you do so -- either by quite literally taking the mid-terms and finals of the classes in question; or by taking an equivalency exam; or by preparing a portfolio wherein you challenge the class by writing down and proving your knowledge. It just depends on the university.

Once you've picked a college, talk to the admissions people, and to a counselor in the major you have in mind, and see what can be done.