i charged businesses and home users separate fees, all hourly, starting from when i left my house, or when i started repair at my home. my "pc solutions" ads might still be floating around in googles cache. if they didnt like the rates, i didnt waste my time. for home users, my turnaround was always same day, if not overnight; nothing took in excess of 2hrs, 90% of the jobs was 30min-1hr. When i returned the call stating it was fixed theyd be shocked... well, when you do this for a living, you've seen it all (started pc tech repair work bout 15yrs ago).
most computers are too friendly these days so, anyone can basically repair them on their own. more importantly i dont like the rates, and neither did the customers, so i dropped it. ie i'm not going to spend 2hrs of my time to hear someone gripe about prices and treat you like a low paid highschool kid and want edumacated on something they can look up themselves (they'll demand this as free work from you) or ask any teenager to fix. even if they dont want to pay to get it fixed, its cheaper to buy a rig thats new, and get a warranty on it. but you cant replace custom rigs with local tech support (my "bread and butter)... but these customers were gamers/sysads/engineers anyway who would eventually (read: have time) learn the ropes.
to sum it up, its been a field going downhill for years. just look around you, specially overseas. if still interested, once youve built your user database, have a perfect and standing record, they'll do the advertising for you (i still get calls from previous clients). This was eventually the majority of my work (loyal customers who know what i do). Same day repairs, honesty, courtesy; my formula. Clients did not really care for pricing once they've seen your work (and your pricing is reasonable).
also, you might be interested in those businesses who will do all the client/calls, and you do the work (less money for you, but youre not looking for clients)... my intention was to not do this low level/tech/"grunt" job for a living... but if you're looking for somewhere to start...
in the case you havent already gotten your credentials, start with the CompTIA A+ and Network+. These will get you started at least. You'll eventually want the MCSE/MCITP/desktop repair certs, otherwise you'll be just another nobody pretending to be somebody.