Pinetree makes a couple of good points.......you need to know how the surrounding properties are being managed and yes bigger is better but not always possible.
When you go looking for property, get to know some the local residents and discuss hunting with them, you'll learn real quick what the feelings are in that area and it may help you decide on a specific tract of land. When looking at specific tracts, look for cover, water sources and natural food sources. If there is open pasture, then you can plant part or all of that as food plot(s). Even in the end, if all you can afford is 20+/- acres, then eventually you can turn that small amount of acreage into a "Mini Dynamo" of a hunting area for you and your family to enjoy for generations to come.
Remember, your property will become what you make it, the harder you work to attract the deer and hold them close, the better your chances will be at putting meat in the freezer.