You can get a home equity loan on the house, but what will control is the title.  As long as your name remains the only name on the title, then the house will remain your separate property.  If you put her name on the title, and then you later file for divorce, then some courts will find that you "gifted" your wife an interest in the property.  If she only signs the loan documents, all it makes her is a co-signor on a note.