Space -pretty much what you want to give them. We have an area about 15m x 20m which we use as our pig paddock - we generally raise 3 or 4 weaners, starting off with a smaller area and then increasing the range over the time. Essentially the smaller the area the more it will get trashed....
Feeding wise - the rule of thumb is 1 lb hard feed for each month of age - generally divided for feeding in 2 lots each day. IE a 2 month old weaner will get 2lbs food a day.
Caveat - some people feel that the max amount to feed is about 5 lbs a day otherwise they can run to fat (depends on space/breed/other food they can forage)
Enjoy!