Start preparing now. Whatever paper and pictures you present to him becomes official record.
Don't worry about the carport or the occasional glass of wine. Is she safe? Are your mom and her BF safe? Do they have addiction issues? How's your job? Think: Safety, Sobriety, Dependability, Routine, Education, Good Priorities. S/he will be looking to make sure she is clean and lives in a clean environment, that she has toys and books, a safe place to sleep, etc.
Are you in counseling? It was a lifesaver for me during both processes to have a neutral someone to turn to to help me decide what was unnecessary anxiety, and how to solve the issues that actually merited my attention.