I’d actually guess that 10 acres would be a minimum, in order to account for unusable areas and unforeseen needs for expansion. Now, anything much over 100 is probably pushing it, unless a majority of it is unusable. Besides, if eco-tourism is even a small part of the plan, it won’t help the travel brochure much to bulldoze rainforest and use every square inch of land available. So, 10 acres minimum and 50-100 acres desirable but budget considerations and site-specific conditions trump all else… in my opinion.
I saw those massive land offers for 12000 acres. It’s both too much land and too costly. It wouldn’t hurt to ask about splitting them up but I’m guessing they’re only that cheap because it’s in bulk and would be hard to sell at all otherwise. The intended market for land like that includes land developers and resort operators who want to build planned communities with 18 hole golf courses and the like. The other issue could be access. If you subdivide a piece of property, there’s always the issue of one party or the other accessing their land across the other plot. It all depends on how you divide it and where the road is, though. I think the per acre price could easily double, triple, or dodecadrupple if you don’t have to take the good with the bad and/or cut into the nice, round promotional stats of the real estate companies. (ie. reducing the ocean frontage of the remaining parcel)