I don't very many primary shooters that don't allow their second shooters to take copies of what they had shot for self promotion. I allow anyone that has helped me to take copies but I also warn them about trying to sell the images.
You have received some good suggestions so far. I know a person that wanted to fast track his entrance into this market and went to a modelling agency and hired himself a bride and groom. It cost him close to 1200.00 for the day but it allowed him to take his time and he came out with some outstanding shots. If you want to be a business you have to act like it and sometimes this means investing in your future with things like this. I know many that simply like to go to family and friends weddings for the sake of expanding their portfolio. Just remember not be a burden on the primary photographer.