Dogs have a massive impact on your life, especially during the puppy stage when they really can't be left alone, and even an adult dog can't be left for longer than around 4/5 hours at a time.
It's a baby animal that, as pp said, that doesn't wear a nappy and in addition is going to be bitey and chewy for a while.
An adult dog is very different from a puppy, so looking at your in law's dog is not going to help you much at this stage. Cockerpoos can be quite hard work and a bit crazy, obviously, being the mix that they are, but well trained, they can be lovely dogs.
If you've done as much reading and homework as you can about what to expect and so on, and have a pretty good idea of what having a puppy involves then it shouldn't come as too much of a shock.
Puppy doubts are very common, it doesn't necessarily mean a dog is not for you - lots of similar posts on here - and 'puppy blues' are a real thing. But if, like your in laws, you put the work in, you'll end up with a well trained, lovely family member.