It’s a tough question because manufacturing equipment is just stupidly expensive (a good end mill can upwards of $500) and usually out of reach for the average consumer. But if I had 15K to buy equipment I would probably buy a CNC plasma cutter and a Tormach PCNC. But if your budget is 15K, you need to save at least 5K of that for material and consumables. Especially if you’re trying to scale, you’re going to have to account for rejects.

If you want to learn more about manufacturing techniques , this is the book I used in college which had a great breakdown IMO https://www.amazon.com/Fundamentals-Modern-Manufacturing-Mat...