The drug dealer is on my fiance side of the family. I don't have any other place to go so.
Okay. Your fiancé's brother is the drug dealer and the house belongs to the drug dealer's family.
The house - and you and your fiancé if occupying it - will still be under police scrutiny. Having a drug dealer in the family unfortunately can adversely affect the whole family.
If the house is the only place you and your fiancé have to live in, you will not only want to clean the house thoroughly, you will need to be careful who visits you in the house.
I would worry about your fiancé wanting to entertain his brother at the house - making you vulnerable should the police come looking for him. In addition, you may have the brother's friends and acquaintances showing up at random times looking for drugs.
View the video whose link was provided earlier to learn how you should interact with the police if (or more likely when) they knock on your door.
Good luck.