Double Majoring in Psychology (I-O) and Advertising?

How hard would it be to double major in these majors? Is it difficult to major in two majors in different colleges?

It is not easy seeking a major from two different colleges. You won’t be able to apply for the second major until end of first or second year but you must meet any course requirements for a degree from both colleges, meaning you need to start taking courses needed in freshman and possibly sophomore year in the other major along with any required courses in your psychology major even before you apply and find out whether the other college will accept you for that second major, and there is no guarantee it will accept you even if you have high grades, although that often raises the chances significantly.

Moreover, to graduate you must complete at least 30 semester hours more than the graduation requirement for your college in your first major. Thus, instead of the 120 semester hours needed to graduate in psychology, which averages 15 hours per semester over 4 years, which is considered a normal load, you would need to complete 150 hours, which means an average of about 19 hours per semester over four years and they will not even let you take that many hours first semester, freshman year. In other words, attempting to to do a double major in two colleges usually means that you will need more than 4 years to graduate.

Also, you can get issues of conflicts that do not arise when seeking one major. For example, it is not all that uncommon for someone attempting a double major in two colleges to find that in one of his semesters he needs to complete a required course in one of his majors and a different required course in the other major, and each of the courses is a prerequisite to taking some upper loevel courses in the same major after that semester, and he discovers that the two needed courses are offerred only at the same time during the semester and there is no solution except to try to pick up one of the courses in the summer.

In other wordfs, it is possible to do what you desire, but do not assume it will by any means be easy.

Can you use summer courses at community college and transfer them in to cover some of the reqs outside the two majors, like gen eds?

Yes, CC courses that are accepted for transfer to UIUC (not all are) can be taken during a summer to meet gen ed requirements.