Well, you don't want to get ripped off, do you?

Per hour is generally a good rough idea, but you should quote to the client how much a job could end up costing, before you get a work order.
So, estimating how many hours a job may take, you have a rough idea of how much you should charge. It's up to you what your "hourly cost" may be (Depending on your skill it could be in the range of R80-R300 per hour, and I'm sure there are guys who can ask for much more easily, but they are highly skilled and well experienced)

Unless the client is making the offer of course, if a client knows where to find the talent at the right price, in all likely hood they'll be setting the fee structure.

In any freelance situation, it's a good idea to request at least 50% upfront.

A fully completed model and animation, with lip sync could take a very long time to complete by yourself, depending of course on the quality of your work and the length of the animation. Possibly there are guys who have a "price/length of animation" charging method, but i've never heard of it.

Good luck :D

Stuart Coutts
scouttsart.blogspot.com