I'd advise - do the boring stuff!
Forget the joy and "greater purpose" of e.g. keeping animals you enjoy.
Read up on commercial farming - what are local costs? What kit do people use? More importantly, what could apply to your situation? E.g. I know that big-bale hay is more cost effective but I don't have kit to handle it - yet. It's something I've filed away as a future priority.
Ditto current concerns around vet meds, wormers, legislation changes.
Look up standard business stuff - banking, VAT, self assessment taxes, accounting / book keeping. Even if you only have 3 hens to start with, have a "business hat" on. Track expenses. Lower expenses - to a point. Be brutally honest with yourself about what you can and can't afford, and what would be viable.
What are local facilities e.g. slaughterhouses, markets?
What are the environmental impact of your plans? Do you know about soil health, water quality?
If you're in England, AHDB have a Better Returns Programme which have good basic guides to lots of things. Obviously the concepts can apply in other countries but the exact legislation may differ. Similarly, in Wales there is Farming Connect.
Allow 5 times as long as you think for paperwork, I'm just setting up, I thought I knew the system but yikes!