How easy is it to tranfer to another college… For example, from the College of Science to the business scool?
Very easy! You can even request it on your myNEU portal before getting to campus. Once on campus, a change is usually very easy as well, taking at most a single semester to be official, but you can even take classes before being an official major. There are very few restrictions between the colleges, though there are some. That said, a friend of mine applied undeclared, switched to Bio for freshman year, and switched to business (and took business classes) starting his second semester - by his third semester, he was in the business school officially.
This goes in general for taking courses across colleges in general usually too.