(not an expert, but based on my research to date:) 50' is borderline (one competent captain, potentially the owner, and one of the passengers helping out at times; of course if you're doing passages, etc you need multiple humans for 24x7 watchkeeping, even if one of the watches is held by someone only competent enough to wake the master. i.e. it's just at the limit of what a couple can probably manage themselves. 40-45 is probably better for that, but for passagemaking across the Pacific you might want bigger, and for group charter use bigger is somewhat better, especially since when you charter you almost certainly will have 2+ crew)

80' is absolutely full time paid captain, full time paid mate (potentially engineering or water toy support), and a steward/also mate-when-needed. If it's being used fully, probably need 2-3 other crew for rotation, and potentially would go 3+1 for a heavily chartered 80'. The paid captain at 80' is not merely for driving the boat but also the management of staff, maintenance scheduling, charter management, etc.

80'/24m is also where the commercial regs come into play (which I'd probably be trying to meet anyway), and 80' cat is already going to have a hard time with marinas in a lot of places (due to being wide, as well as long), but due to solar + good watermatermakers + excellent tenders, could probably operate at anchor far more than otherwise.

I'd probably do the "Boat DAO" model with the 80' and have 4-6 rentable cabins (not true retail, but within friend network, etc, and more particular when I'm using it). This is the specific boat I want: https://sunreef-yachts.com/en/launched/sunreef-80-eco-141/ (although by the time I'm in a position to order, and wait 2-3 years for production, there may be something better, and I'm hoping Starlink, lithium-ion batteries, etc. continue to improve -- mainly from a cost and maintainability perspective.)

Part of my motivation is that some of my friends are doing a lot of Seasteading related stuff and I'd want a boat to be able to visit/stay during some of those events using fixed platforms.

Would probably run Caribbean (where I live) from mid-NOV to mid-MAY (hurricane season avoidance), and then summer in Med, for at least a year or two, then do 2-3 year RTW journey once or twice. My plan would be to personally occupy it ~3 months out of the year at least, and to be able to charter entire boat or individual cabins for enough to defray most of the operating costs if successful. Spending the next couple years getting familiar with sailing around the Caribbean as well as obviously earning more money to be able to afford this ($3-10mm capex, 10-20%/yr of that also total operating budget, although some fraction comes back as earnings). I think I could realistically crowdfund/investment contract ~50-75% of this as well if the business model works out, maybe through prepaid/discounted use. I might get a ~30' powerboat here in Puerto Rico since <41.5' can be lifted out of the water and put into a warehouse rack during hurricane season, and powerboats are far more useful for day and 1-3 day trips around here due to currents/winds. Something able to get to Vieques/Culebra/Culebrita and maybe to USVI or even BVI.