When you want to apply for planning permission for a house you will need to pass the 3 tests outlined below, to show that you have a viable and sustainable long term agricultural enterprise and are not just a speculator trying to get planning for a house.
The local planning department will want to see that the business has a long term future and that it is on a sound financial footing. This is normally demonstrated by an additional investment in the enterprise by way of new buildings or diversification. All of this and more is covered in the book.
This is to demonstrate that there is a need to live on the land for the welfare of the animals. These animals must be the right type of agricultural animal, for example sheep would not qualify as they have a lambing season. You can live on the land during the lambing season but you wont get planning for a house. The animals must be agricultural, and you need to be able to stock enough of them to make a living. The book tells you which enterprises are suitable and which are not, and what to diversify into to make it pay.
For planning permission to be granted for a house the Smallholding must be viable. The viability test is that in a specified period of 3 years you must earn at least the minimum wage for 1 of those years. The amount of money you earn in that period will be commensurate with the size house you will be allowed to build. On the minimum wage it would be a small house. This is regardless of your personal wealth, the more money you make the bigger the house you can build. The book shows you how to make money from a smallholding.
For a more in depth look at how to make money from your smallholding you should consider reading Real Smallholding which explains how to get every penny out of your investment in your land. From choosing complimentary small farming enterprises to saving money on agricultural machinery.