I have a good friend who does kitchen units fitting and he works with a neighbor
He is always busy and does other joinery work as well He worked for a Barfitters as a Laborer/joiner and was laid off but put a few Ads in the Store offering to put together Self assembly units and one thing led to another has got work, and has had to turn away jobs, so He got his Pal and another guy helping him out
All he charges is a fixed sum for the job plus parts at cost plus a few pennies, unless The part are already there.
And people have given his name to their friends and its Just snowballed

There is also another 2 Guys who do electrical and Gas Repairs (certified) and they started the same way and the word of mouth about their workmanship has got them recognition.Now they also do Subcontract work for their old Employers

On the Flip side If they do a bad job or rip off people over a job News travels fast
There's somebody in a nearby town who would try to sell you a whole roof without inspection and for perhaps 1 cracked tile!
and often had been known to pocket the money and claim poverty /or disappear

and jack up the Price Now when he did do the work the entire roof was left in an unsafe condition meaning another reliable person has to risk their life to try put things right by stabilising the roof or more often condemning the "workmanship"

Has been"featured" on Both the Consumer Watchdog programmes(BBC) and the House of Horrors(on the other channel)
Yet he's still in "Business"
WOW The Second opinion/Improver type of checkup service is a very good Idea