What is the difference between "start up" and mere "start"?
As I know, "up" has the connotation of "perfectly", but in this case it may not be the case.
8)When the brothers were 18 and 22 years old, they started up their own printing press and bicyble shop....
"Start up" is almost universally used to denote the commencement of a new business venture. You are correct in saying that simply "start" would do as well, but that is not the current usage.