If you are going to be doing commision work at weddings and barmitzvahs etc, then you can probly include your exclusive rights for the reproduction and copying of images within a simple contract/agreement with the party you are going to be doing the work for.
That way you can, arguably, maintain a degree of ownership over your work, and capatalise on any additional copies if required. Presumably you will use a digital medium, and only provide the customer with high quality prints, keeping the original files for your own records.
Be careful though and make sure you back everything up, I think wedding photographers have been sucsesfully sued for losing images. Its all about the paperwork like everything else. A good contract that protects your interests is essential.
Regards
Alan