A good resource for providing a breakdown of feudal lands, and if you're unused to the feudal system, it provides great background. I think its math could be better organized so that the income and expenses are put next to one another, however. The Stronghold Builder's Guidebook from 3.5 ed, for example, just presumes income and expenses match unless there's a special feature of the stronghold itself, and you get a clearer sense of what you're paying for with the expenses as functions of your stronghold require set numbers of workers. Used together, however, if DM and players aren't afraid to break out an accounting book, this could be a really interesting means of producing a stronghold.
The examples are a little confusing, however. There are way too few sheep producing income for how many acres they were placed upon, for example, and I don't know why the priest is getting 46 acres of land for his service. How much annual salary is an acre of land worth?
I'd suggest expanding this to other cultures, such as Dark Ages pagans or other "barbarian" tribes, or Iqtas or other Asian systems, for players who aren't always stuck in Fantasy Europe.