A beginner beekeeper should start with a minimum of 2 colonies.

Why do beekeeping instructors recommend a beginning beekeeper start with a minimum of two colonies?

Starting with two bee nucs or packages, and not one, enables a beginner to compare the progress of two colonies, and to judge better if one is encountering a problem. Many problems can be resolved by adding resources – feed, a boost of a frame of brood from another colony, etc. By comparing the two, a beginner has a better chance of realizing that one colony has a problem in time to resolve it before losing the entire colony, perhaps has time to replace a missing queen or recognize the signs of disease. Also, if one colony suffers a predator attack and is too small to survive on its own, the surviving bees may be saved by merging with another colony.