you could also use some public liability insurance... which basically covers you harming anyone else with your work...
if you're teaching someone how to setup networks then you are going to need professional looking (and professional written looking) documentation.
scribbling a few addresses or protocol/service names on the back of a napkin isn't going to cut it...
you also need to really *really* know your stuff...
when someone comes to you saying that they have trouble connecting their windows 98 machine to the windows XP machine and sharing files/printers, but their windows XP machine reads fine from the windows 98 machine (a very common problem) you need to know *exactly* what to do... without going to google.
if you're fixing PC's you also need to be aware of the context of what you are fixing and the legal implications.
like if they have child porn you need to report it.
if they have confidential files, then you need to respect that confidentiality.
you also need to be aware of the costs involved in recovering data and exactly when to stop when things start to go wrong before they are irrecoverable!
(for example I recently had a drive problem and lost my entier music collection and all of my course work from Uni, as well as a lot of the installation files and activations codes/licenses for software...).
I estimate the cost of this would be, a few hundred ££ for the software.
in time alone copying all my CD's back to the computer it's cost another few hundred.
and the nature of the university notes and course work mean that they could never be recovered, but they cost ~£10,000 to acrew... basially if you were fixing my computer and accidentally deleted a partition whilst trying to diagnose a problem or the computer crashed whilst resizing a partition (as it did in my case), you would be entierly shafted...
the size of the claim that I would make against you would (most likely) far outweigh your liability insurance, you're a minor and your financial guardians are your parents...
assuming you broke my PC could you folks really afford a £11,000 bill for data + £1,000 for data recovery + however much in court costs...
I know that I don't have a spare £20,000 ($37,600) just lying around. and whilst I know absolutly nothing about you. I'll hazard a guess that neither you nor your parents do either...
(the end of the story is that I have all my data back. but have had to buy forensic data recovery software to actually get it back!).
also as joxley said...
if a 15 year old turned up at my door I'd probably send him away else my neibours would think I lure kids to my house!
im just gonna do neighboorhood stuff, jeez guys
probably should have read that before I wrote all that stuff above...
just doing it for neibours is a great idea...
but like a I say bear in mind if you mess up you could cost yourself (or your parents) a friendship, (and still possibly money)...