I keep reading that people start out with two nucs and before the year is out they've had to split and end up with 6 or more hives.
A lot of this is because of either swarms, or swarm control. When you read about swarm control, there are two main methods applied. First is split, second is 'give them space'. The problem for the new beekeeper, a box of brand new frames may look like a lot of space to the beekeeper, to the bees, it's just a bunch of things with no comb. Bees dont view that as space, they view empty drawn comb as space, and in the early part of the season they will want more space then the amount of comb they can draw. The lack of comb leads to swarm preparations, and then splits to try prevent the swarm.
The other thing one notices about new beekeepers, they tend to be eager for 'free bees' when and will jump at the chance to go chase a swarm.
This all adds up to 'start with one, end up with 6'.
If you dont want to end up with more colonies, read up on ways to prevent swarming that dont involve making splits.