If you were offered a small amount of money to reside in a house with people you didn't know or had not seen in years, would you take it?
The Ministry of Magic is conducting an experiment and they need guinea pigs. They place an ad in the Daily Prophet which reads:
NEED SOME EXTRA MONEY?
Come experience life as a Muggle! Boarding and compensation are provided! Hurry, there are only 16 spots open. Inquiries can be sent to F. Crofton at the Department of Muggle Relations at the Ministry of Magic.
Once the 16 were selected, they were sent a letter that explained the guidelines of the experiment.
Our House is a post-Hogwarts Harry Potter RPG. It can be assumed that although this is canon compliant it's grossly AU.