It depends (I live in the tropics) - you are better off looking at each piece of
land, and evaluating its assets. Is there a river? Well that means you might have a ready access to protein. Are their springs? You may be able to make your own
pond.
Conversion rates to protein (which in the tropics is the hardest thing to produce, starches are VERY easy) for fish and
chicken can be 2 to 1, whereas
cattle is 10 to 1. Goats will eat (prefer to eat!) what other animals don't. Mine eat pretty much exclusively large leaf from brush, and bark from saplings. The only
feed they get is to keep them busy while milking them. My
chickens live on bugs and coconuts and do very very well (lots of eggs, big fat
chickens). They also get the waste from cleaning fish and all the scraps from the kitchen.
My total feed bill for the month is less than 10 dollars.
I am using about 3 acres I think, and not very effectively - but then again, I have hundreds of acres.
Get land with
water, and is fertile - not all land is created equal. Of course if you can find land that has been owned by a subsistence farmer, who has planted fruit
trees, etc, you are way ahead!