If you go back through the posts on here you will find lots old posts where things go wrong for people because they have not invested in the training.
there is a lot of rubbish on the internet and you do need to be able to tell the good advice from the bad. There are a lot of cleaners on here that think that you can train a monkey to clean carpets, believe me you could train a monkey to clean carpets to the standard that some achieve.
The £500 earmaked for a machine would be better spent on training to give you an insight as to what you do need to do things properly.
The carpet cleaners carnival is on the weekend where for £24 you get the opportunity to attend some very good advice giving seminars, by industry experts. There will be machine and chemical distributors. It would be a good insight into the industry. The machine that you put a link to would be a bit of a joke for a pro to start up with, but there are probably loads with that type of equipment on this site looking out for free advice, that know no better.
Peter