I have a clause in all my contracts that gives the client ownership of all the "work", i.e., graphics, text, programs, as soon as they make their final payment. IMHO you'd be foolish to accept anything else.
On the other hand, the contract protects me too, because I had one person who didn't pay me after his initial deposit, so I rescinded my work, as the contract permitted.
It's tough to deal with strangers. Contracts help.
For more, see
http://havingmyownwebsite.net/sitedeveloper.aspx