Moving Sims out of one house and another family into it will not cause any neighborhood corruption.
Bulldozing a lot that does NOT have graves on it will not cause any neighborhood corruption.
It's only when you do things that can mess with character files that cause neighborhood corruption. Deleting Sims, putting occupied lots into and out of the lots bin, etc.
The funny thing about neighborhood corruption is that it doesn't progress at a standard rate. I like to think of it as a time bomb, but you don't know the time left. Could be 10 days. Could be 10 years.
I had a neighborhood give me horrible signs of corruption after 1 generation from doing things that caused corruption. Went back to a back up that was about 1/4 of the way through the generation. Didn't get major signs of corruption again until about 6 generations later.
It is however, something to keep in mind so you aren't suddenly surprised if one day trying to load the neighborhood causes the game to crash (that's end stage, but you typically get other problems that cause you to abandon the save before it gets that badly corrupted).
It's nothing to go into a panic over if you realize you've done it, because with a decent back up schedule, you will likely be able to play the neighborhood for as long as you want before things get too bad. But getting caught without back ups after you know you've done things that cause neighborhood corruption is not something I would want to happen to anyone. Especially to someone who had gone multiple generations in. Learning to not do things that cause neighborhood corruption and keeping decent back ups if you do, is not a lesson you should learn the hard way. Trust me. It's upsetting to realize that your neighborhood is badly corrupted. I learned this lesson the hard way.
Now lots that have been lived in for several generations may have some wonkiness that replacing it will help and long lived Sims with a ton of memories may develop a jump bug (I've never experienced it or researched it so I don't know how bad that is).