Using comps correctly

[Fred Forgione]

I am in the process of pulling active and sold comps on a ranch and there is nothing on the market like the property.

Property:
Ranch, 12 rooms, 5br, 2.5baths, 4000sq. ft, 3.8acres.

When no real comps exist, I am uncertain if I should pull comps then based on the house or the acreage. I can find comps that have the same acreage but the houses are completely different and I can find similar houses but the acreages are not close. Any help would be awesome!