So you want to make money with your knowledge of computers? You can do real well, but i cannot see you making anything over the net unless you can get a job at a site that charges for help.
Your best bets is to put a few adverts about close to were you live, go to your local corner shops and ask them can you put an advert in there windows. Costs about 7pence a day.
Put soemthing like this.
NEED COMPUTER REPAIRS OR UPGRADES OR LESSONS
THEN PLEASE PHONE XXX XXXX XXX OR EMAIL ME AT XXXX@XXXXX.COM. CHEAP RATES. WILLING TO DISCUSS PRICES TO FIT YOUR BUDGET. CHEAPEST IN TOWN
You wil be surprised how quick you will get phone calls and emails.
You can do very well over the few weeks you want to do it..
Good luck.
And because it would be working for yourself, you need no cerificates..