Confidentiality and home meetings: Homes enable private controlled spaces that can be configured to your needs. Homes can also be targets. People pulling up in front of your house is bad if you are being targeted.
Computing: Use a 400 Dell Optiplex like system offline with no wifi and no Bluetooth. This protects against attacks with real air gaped systems.
Team size: Teams are 2 people to 5 people max including yourself.
Security from physical attacks: Defense is mostly about perimeter security and active defense upon breach. You can only defend so much without fencing and razor wire. This fencing and razor wire makes you a target.
Guidance from the pros:
https://www.dni.gov/files/Governance/IC-Tech-Specs-for-Const-and-Mgmt-of-SCIFs-v15.pdfThe legal question: Build all you want. Train in defense all you want. If you defend yourself, the state will still target you. Now what? Defend yourself from an attacker, but now Police kill you in a raid.