Basically it's a messy job, on occasions dealing with nasty smelly stuff. Apart from a strong stomach, you need a fairly high powered pressure washer, a long drain jetting flexi hose, jetting nozzles, supply hose / bowser plus Bailey rods and all the attachments. You also need to be able to identify when drains have likely collapsed and determine the location of any failure / unclearable blockage.
On the plus side, because it's often an unpleasant job you can make a lot of money out of it quickly. My minimum charge for anything which requires the machine is £50 to turn up and nobody has ever complained.
The most expensive piece of kit is of course the pressure washer which will set you back at least £400 for a basic second hand model powerful enough to do the job. (A £99.95 one from Halfords won't!) New ones are about £1,000
Of course drain jetting is just one service offered from my business portfolio. You can go for weeks without being asked, then get a load at once.
The best customers are the commercial ones - farms, business premises etc as they get you back on a regular basis and the jobs are usually big enough to take at least 1/2 a day.