I get list of new tools I'd like every job. But forget and just get it done with what I have most times. Last year I spent ~$10K on shop supplies. I now must get ride of sometime to get any thing new in, just out of space.
I do have expansion dreams. But takes $$$$$
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The other issue is time. I spent the week on this and not done yet. Don't even know if efforts will bare fruit.
At one point in life I was doing what you do but with BMWs(on a side). Had steady customers, etc. Was thinking about shop. Truth is - if you like what you doing - keep doing it. Making it a business is very different. You will have to charge as other and you won't mess with cars like this one. You won't spend hours and hours on those "front knuckle services". It's only done because you like it.
And only people who really love their cars will pay for time you spend doing it.
You will find that restoring brake systems, electric motors, etc don't make any sense because when you save customer money in parts and it fails - they will come back unhappy. So, there is huge difference between doing service to enthusiasts and getting bigger shop.
You will find that straight jobs that you don't like to do probably make most money. Anyways, if it's hobby - keep it this way. I did and I'm very happy as I still wrench on cars and enjoy doing it.
I am thinking about getting my own tire mount and balance machines as its only thing that I take my cars for and it's expensive, time consuming and they still can screw up.