I can't help you with housing, except to say that some places have a minimum length of stay. I will say, that if you are accustomed to the BVI beach bar scene, you might not be happy on St. John. Because of the national park, most beaches are fairly pristine. Cruz Bay has beach bars and restaurants, and on a few beaches you can get a drink, but for the most part St.John is picnic and cooler territory- no glass. You should rent a car for at least part of your stay, public transportation won't take you to some places you might want to see.