As for someone who took their hobby (photography) and took it from just that, to a full-time, self-employed career, I will say it can be a bumpy road. I absolutely love my job. I didn't make a dime for the first few years, everything got reinvested into gear and computers and insurance.
It seems like you already have the equipment.
Now for some overly personal questions, bare with me.
How is your debt? Do you carry a balance on credit cards or do you have a car payment or mortgage or anything like that? The closest you can get to "debt-free" the better. It will be easier for you to qualify for a small business loan if you need to, and it will reduce a lot of stress during a "slow month". There will be lots of "slow months".
How much do you have in the bank? We have 6 months living expenses set aside for emergencies. Not everyone is as anal about as we are, but it's a safety net. Are you married? do you have someone else contributing to your household income? That can make things easier if you're not the sole provider.
How is your math/accounting skills? You'd be surprised by how little of your day would actually spent making parts. I only spend about 10% of my time making images, but photography is a full time job. Until you can pay someone to do the accounting/billing stuff for you, you'll be doing it yourself. The better you are at it, the less time it will take.
What about distribution? You may specialize in making one-off custom parts, but you should try and come up with something that is reasonably universal, that you could partner with an established shop like Dime City Cycles for distribution. Kind of like they do with those loaded gun rear sets, or the fibreglass tanks. Something that has your name on it, that everyone can use. That's called Brand Awareness and it will help drive people to your website to contact you about building one off stuff.
You don't need to answer these questions on the forum, obviously, but you should spend some time and think about it. Personally, starting my first cafe build and living in north texas, I am thrilled to have such a craftsman like you in the neighborhood.
If you have any questions about things like sales tax, or need a good accountant in Ft. Worth, let me know.