What are the typical commission prices for freelance work? For relatively simple models, maybe even simple animation.
Maybe go and look at freelance websites and get depressed how low some pajeets are willing to work for.
Typically I provide an estimate for how many hours I think it'll take me to complete a task. Forces me to setup a timeline and let's the customer know where all the hours are being spent if there's multple stages to the task (modeling, texturing, rigging, animating). In terms of rate, that's really going to depend on the client. Do some research and e stalk them for an idea of the potential funds they may have. Your client could be a VP at a tech company, or some kiwi with barely a dollerdoo to their name. Just make sure it's higher than minimum wage. No one will respect your work if you're charging them $8/hourly.