Model Release Form Question

[Hamster]

I have had a search and I can't see my specific questions answered so I hope this is new and adding to the pool of knowledge.

The scenario is, I suggested that I take some pictures of an acquaintance, they get some pictures, I get to try out new things. So far so good.
Pictures are taken. I would like to make sure that these pictures are available to me to use commercially should someone, for example say, hey, that photo is great, let me pay you lots of money to use it in my international advertising campaign. Unlikely but ......
I would say that since I said "how about I take some pictures of you" that I haven't been "commissioned". Also the Arts Law link re copyright in the sticky above says
"Some commissioned works: If someone is paid to take or make a photograph, portrait or engraving for the private or domestic purposes of the person paying (the "commissioner"), for example wedding photographs, the commissioner owns copyright in the work even though the artist or photographer is not an employee.The commissioner owns copyright in a film or a sound recording made for remuneration or some other form of payment."
and I haven't been paid anything.

First question is, does commissioned mean some kind of payment has to occur? That's how it reads to me.

But irrespective of the technicalities of the word commissioned the model could claim otherwise later, and another model may want to go into a TFP arrangement with me, and so a model release form is the way to go.

The AIPP has a model release form which I could use (http://www.cpsinc.org.au/photographe...el_release.pdf).

OK, I change the wording from "I understand that I do not have any interest in the copyright to the photograph(s) norshall I receive any further payment." to "receive any payment" and it seems to be pretty good to go.

From my side, I'd like to make sure the model doesn't sell the images and when using them credits me (really, I'm not that fussed re credits right now, but lets say I am).
My question is, what if my model says, "hey I read something about a model suing a photographer for using a photo in an advert where she was depicted as having HIV, and there was another one about porn sites. This form you're giving me to sign says you can use this photo how you like."

I'd say she's got a point. So what assurances can I/do I give the model? Are all model releases the same and the model just has to take the risk? How do I respond to that question from the model? I can see how, from a non professional model's perspective this could be a bit scary and she might shy away from me coming at her with a model release form.