for freelance work, i charge a casual flat rate of $150/hour with a camera in my hand, $75/hour i spend in front of a computer, $0.75c/km mileage and any other out of pocket expenses.
repeat/regular business clients get substantial discounts.
What kind of discount for a regular client. and how often would you consider regular?
if i get, say, a job per month from a client and it runs to a full day (8 hours in total), i'll generally charge them a flat ~$800 + mileage + expenses.
if i'm getting a job/week from them, that would drop to ~$400 for the day + mileage + expenses.
it also depends on who/what the company is. Banks, for example, NEVER get ANY kind of discount. they pay full whack regardless of how often I do work for them.
if the client is a good mate (or a nice bloke who needs a hand), they get even bigger discounts. the last job i did for a friend (bunch of pictures of jewellery etc for an insurance company) it only cost them a case of beer. which they helped me consume.
please note: i never include prints in those costs. when they pay me, they get a bunch of discs with ready-to-go files on them.
My clients never get the images until i get the $$$ (i've been burned too many times in the past).
just FYI: i can get away with charging $150/hour because i have 18 years professional experience, a wall full of professional awards and $70k worth of gear.
i'd actually suggest, seeing as this bloke is a mate, offer a straight swap.
you'll do a days work for him for expenses only and he owes you a full service on your car, for the cost of parts only.
mind you, get him to tell anyone who asks "gee, he charged me a fortune, but it's worth every penny".
good will and word of mouth early on in your pro career is worth more than a mere days pay.