When you are writing to congratulate someone for moving into a new home, there are many wishes to send to them.  First, tell them how happy you are for them that they found a place to make their own.   Tell them that you wish them health, happiness, and many wonderful moments, filled with the love and the affection of family members and friends.  Say that this is a time when they are realizing their dreams of home ownership, and that they deserve to be extremely proud of all that they have accomplished.  Suggest that they keep a journal of all the things they do, to make this house a great home.  Offer to help with anything they might need, but mostly, just let them know that you wish them good fortune as they make this positive change in their lives.