Is it bad for Feng Shui to have strangers living in the new house?

On the contrary, the more the better.

Have you ever heard of the phrase "Wen Ju"? Even when the house is newly built, it is good for someone to come in and sit down.

So is the new house. The more people come, the better, preferably people with long life or children.

Ha ha, don't worry, it's just a good thing for strangers to live in a new house, not a bad thing.