This post will be cross-linked with my capital building guide.
I am contacted regularly by people who want to start building capital ships and have some questions. Often they're interested in starting building with less than the 24ish billion recommended by my guide.
One of them, a longtime reader who has asked not to be named, actually got to production - a rare occurrence for would-be capital builders - and was kind enough to offer insight into his and/or her experience.
The tl;dr is that the recommendation I usually make - buying as many blueprints as you can toward a carrier set, so that you minimize overhead from BPC while still having enough left over to buy minerals - is wrong. Instead, what a new builder should do is build entirely from BPC, reducing startup costs to practically nothing but at the expense of increased overhead.
Here's a new, super minimal startup plan:
1. Find a building station. It, or a station in the same system, must have 50% (maybe as low as 40%, I don't really remember) refine rate. Get 6.67 standings with the corporation that owns your refining station. This step is free.
2. Buy and research compression item blueprint/s. 15m.
3. Buy a capital ship hull BPC. ~30m for a carrier.
4. Buy capital ship component BPC. ~115m for a carrier.
5. Buy minerals. ~1100m for a carrier.
6. Compress minerals. If you can't both acquire and compress your minerals in a highsec system adjacent to your building system, you'll probably want a freighter (1430m) to move things around.
7. Use a covert ops transport (~110m) to move the compressed minerals and the blueprints to the building station. Alternatively, contract black frog.
8. Decompress and build.
Reference my guide for the long versions of these steps.
This method gives a startup cost, for an incredibly minimal, somewhat inefficient, and somewhat pain in the ass process, of about 2.8 billion. I rather suspect it will have scalibility problems, but if you aren't trying to build 14 ships at the same time it should work just fine. Just be careful that you're making a meaningful profit after BPC; once margins on hulls return to normal, those could really eat into profits.