Some people moved in next door and hauled at least 8 computers into a house supposedly they run some kind of online business What kind of online business would you need 8 computers to run?

first of all it would be polite to just ask them what and how they use them for their business. be friendly to thy neighbor

as in this instance a person answering your question cannot answer your question exactly.

however an informed guess you could infer that they where doing a wide variety of things from hosting servers to computer experiementation or application.