There is no short cut to being a good mechanic, for a start you need to be born one and you will never be 'well off'' until you own the garage, doing it as a "good idea" is not a good idea, you have to want to work hard and long at it to become good, most 'mechanics' are really 'fitters' with little or no diagnostics skills and very little experience who have worked their way up in a workshop, changing parts over is not being a mechanic! Above all respect age and experience, you can't buy it!

The BEST way to be good is to start at the bottom with a 3 or 4 year apprenticeship (or at least as a garage 'gofer') with day release college to get the certificates required.
having said all that I have employed chaps (and girls) based solely on qualifications, never again, aptitude and natural skills are as important as the right papers.

I started off at a company called Trojan Engineering in Croydon, U.K. working on Lambretta scooters and sweeping the floors and then they let me loose on Alpha McLaren F3 and Can Am group12 alloy racing car chassis and on to Italian 7.5Ltr.V8 Iso Griffo muscle cars. It still took another two years to land a 'proper job' as a motorcycle mechanic in London working 70 to 100 hours a week for about $50 and I then spent 28 years on Honda and then Kawasaki bikes working up to workshop manager, never 'well off' but it kept me and the family with food and a roof over our heads and a couple of decent cars in the drive.
I then realised I was a bit good at electrics as well and developed that side as it was cleaner and paid better resulting in starting my own firm in 1988 fitting audio and car security for retail outlets and clients, now that did pay well, I have now semi retired in Spain at 55 and life is good, but it didn't happen overnight.
Best of luck and if it’s in your blood, you will be good.

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wisdom is not knowing all the answers but knowing where to get them