There isn't really a simple answer to them!
Rates go from around 55p per mile if you work for TNT up to around £2 per mile if you find the right client.
A good company will give you a retainer, so you get paid a minimum whether they use you or not.
Most people like you to be self-employed and have insurance, G.I.T. (Goods In Transit) cover up to around £40,000 minimum, and your own Public Liability (mine was around £2million).
GIT and PL for me cost around £500 per year through a small village company rather than the big co's who wanted five times that.
Insurance for your bike should go up at least 500%.
Downsides are that you have to work in bad weather, and to make your money as a single person outfit is hard, because ideally you need someone to arrange for you to pick something up at the other end so that you get paid for the journey back as well!
And running costs for a track-focused bike like a ZXR400 are stupidly high.
The plus side is you get to ride on roads you never normally would have thought about trying, and see a lot of the country (err... well i did high speed long distance stuff - if you're a city courier this won't apply!).
And you get to ride your bike as fast as you can all day long!
I suppose the main catch is that the crash expectancy of a motorcycle courier is around 2 weeks on average. And you may well lose your license for speeding or taking naughty shortcuts. I did it for two years, used to cruise at 120 on motorways (if i got bored I'd speed up for a while!), and never crashed!
I'd do it a lot differently if I did it again, but I don't regret it!
