Dude once the word of mouth gets around you will build a following as long as you do the job and do it cheap. LOL
If you plan on staying in business long you can't be to cheap.
There are people out there that are willing to pay more for great service.
To provide great service you need to know what your doing. This means you need to be experienced and it takes time to get experience. You also need to stock parts so you can complete calls the first time around.
Second trips back don't make customers happy and they cost money.
The people that are willing to pay for great service are also the ones that pay you on time.
Seems the people that are always trying to save a buck are also the ones I have a hard time collecting from.