jess...
...if you are ghost-writing, you get no credit and are only paid for the job as agreed... even if s/he didn't contribute a single word, your name will not appear anywhere and the by line will be:
by Joe Doakes
...if you are writing for the person as a 'with' arrangement, then your name goes under the person who's paying you:
by Joe Doakes
with Jess Smith
...in both cases, the copyright belongs to the person who paid you, as it's a 'work for hire' and not a collaboration, unless your contract says otherwise...
...in a true collaboration, copyright ownership is shared by the co-authors and both names appear, with the person whose story it is, usually going first:
by Joe Doakes and Jess Smith
...the most important thing is to have a contract in place
before you write a single word! ...go to the writers guild site for sample contracts and all the pertinent info on sharing credit, ghosting, etc.... writer's market also has a lot of good info on the subject, along with suggested payment amounts and schedules...
www.wga.org
www.wgae.org
www.writersmarket.com
...you should really consult a literary attorney before going any further... it will save you a lot of time, money, and hassle later on... if you have any other questions or need any help, feel free to email me any time...
love and hugs, maia
maia3maia@hotmail.com