When you book a paid llama by the hour when should the pay clock start? When they arrive are once the first shot is fired from the camera?

For me, when they arrive, usually - or at least, from the scheduled arrival time.  If they turn up an hour early, and I'm not ready and they're sat around for an hour waiting, they're not being paid for that time.

10 min after arrival, as all the concepts and ideas would have been discuss and model should be ready to shoot.

*for paid shoots*

thanks guys!

I stipulate that I pay models for time on set, in front of the camera.
My stylists rarely take more that 45 min, if I am employing one. Models do not get paid for prep time, unless it is going long.

We do take short breaks in the shooting, and I do not subtract those from the "set time."

I have been shooting with this premise since 1982, and I have never had a model object.

It starts at the time you agree that it starts.

If you work with an agency model time starts at arrival. Some model adopt this policy for their freelance work.

Since you are paying you can decide when you would like the "clock: to start and if they accept that then that settles it. I would just implore you to settle this matter BEFORE the shoot so everyone is on the same page.

For me, I instruct the Model to be shoot ready upon arrival otherwise, if they choose to not be shoot ready then we start after they are done with the styling that I requested. My styling instruction are pretty clear and I even provide Youtube videos on how I want hair and make-up done. If I'm bringing in a Stylist then I consider that value-added and it's rare that I'm doing a Model-Paid shoot in that scenario considering that the Model is likely to want to do trade compensation when a their make-up and hair are being done.

But you know what would really solve the issue? Negotiate a flat rate for the shoot.

Everybody does it differently.
I know somebody who pays the set hourly rate from the time the model arrives till the agreed finish time. And if body painting is included, they are paid at the same rate from the moment they arrive at the body painters till they are done with the shoot. Did I mention that lunch breaks are not excluded.

Any wonder that models love to work with them?

And then a cheapskate like me comes along, and is then toooo embarrassed to discuss trade.

when you're scheduled to start (and you're not late, obviously)

If I'm paying (usually the case), it starts when the model steps onto the seamless, and ends when I'm out of ideas (unless the time was agreed on beforehand).

I think the most important thing is to set the expectation beforehand. That way there are no surprises for either of you.

As far as whether you should, it depends on what you require before a shoot. I prefer a more natural look, so I ask that they come with simple makeup and hair. If you're looking for something extensive requiring hours of prep, I don't think it would be unreasonable for a model to expect payment.

I can't imagine being an employer and not paying the person for any time I specify for them to be there.

I would surely not work for someone who wants me to be at their property/place-of-business/other-location but not pay me except for the time I'm actually directly with them, and I wonder at that expectation.

Just my opinion, though. Set your own expectations

From the time they are ready to start, should they not arrive ready.

Clock starts when the llama starts to work, that includes doing make up, hair, clothes, etc. If I have to spend time discussing aspects of the shoot or props, that's work for the llama and gets included in her time.

If there's a delay, caused by anyone other than the llama, that time is included in her pay also.

The clock starts when prep begins and ends when I say "that's a wrap". 

I expect models to be late...if one arrives on time I would probably faint. Starting the clock before prepping begins is a recipe for disappointment.