Legalities of Freelance web design

I'm sure most people have had the idea of doing this at some point or another and some have even made careers out of it so I wonder if you could help me.

As a little money making venture I fancy trying my hand at a little freelance web design in the surrounding area. I live in Northern Ireland and the area around me could still be considered very rural and I'm pretty sure there are many businesses who don't yet have websites who just need convicing they need one. My plan is to a) Convince them they need one and b) Convince them I'm the man to do it.

I'm pretty happy with my abilities to put together a pretty acceptable package for most people. I won't be busting out massive database driven global solutions but I can create a decent presence for the company, set up a proper e-mail solution, help them with their identity, advertising and some simple content management if needed. Now the question -

Legalities, what must I do and what must I watch out for?

I was 19 on Tuesday past so I'm not going to want to parade that fact around too much, doesn't give much credability really. I can start a portfolio with a few projects I've done for people I've known but when it comes to strangers then it gets dicey for me, people obviously want come back on expenditure and I want to cover my ass as well if someone decides they don't want to pay me. I don't want to get too heavily into this that I start drawing up contracts and setting myself up as a sole trader or something especially seeing as I'm leaving for Edinburgh in September.

So is there any way to keep it simple for a few jobs that ensures both myself and any potential customers are covered?

Make sure you get pay slips from your jobs.

You need to have a hard copy of any cheques recieved for tax purpouses.

If you are on the payroll make sure you get P45s when you finish a job or P60s if the job goes over a tax year.

You must do your tax return too.

Thats all the evil stuff out of the way