Cruise ships do pretty well. I looked up prices and capacities and found you can build a large cruise ship for about $100K per resident. The biggest ship I foun

Cruise ships do pretty well. I looked up prices and capacities and found you can build a large cruise ship for about $100K per resident. The biggest ship I found could house 9000 people. Seasteads would mostly use aquaculture, so you don't need much growing room on the ship. If you're close to a shipping lane you can trade for other foods you want, just like everybody else does.