Daniel, if you're to be paid for new development then ownership of IP needs definition up front. In principle you own it unless you are an employee (which is not as simple a definition as you might expect) or agree to assign the rights. "Work for Hire" applies to software if you are defined as an "employee" in which case your client owns the rights.
If you expect your client to pay for development and/or if you are reliant on access to their smarts or personnel to complete the work, they may well ask for ownership of the work they are funding. Fair enough, too- if they help you make it good and pay for it, they did that for themselves, not so you can sell to their competitors and make yourself rich ;-)
Check out
http://www.developerdotstar.com/mag/articles/daniels_softwarecopyright.htmlRegards
j.R
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1
