Hi Mike,
In answer to your questions, here's my advice for what it's worth:
1. Training
Look into the NCCA, IICRC, or get a free training course with your machine. Don't start without training first.
2. Machine and equipment
As a distributor of CFR machines I probably shouldn't say this, but spending £2500 on a machine if you're on a tight budget would be madness!
All you need is a decent, reliable entry level machine (at least 2 vacs + 100psi pump). A more expensive machine won't clean better, only faster (a good operator with a 100psi machine will clean just as well as a good operator with a £20,000 truck mount. It will just take him longer!).
3. Van
In terms of space, you might be able to fit what you need inside a car. However, it may be harder to get people to hire you if you don't have a van. It doesn't need to be new, just clean and tidy.
4. Marketing
Leaflets and door knocking are very good ways to get work without spending a lot. A good distributor may be able to advise you on what other low cost marketing you can use. Also do a search on this forum.
Don't expect to make much money to start with though, it will take time to build up, but the rewards are there if you get it right.
Hope that's helpful,
Matt