In Animal Farm, what is agreed upon regarding the farmhouse?

The animals agree that the farmhouse will be kept as a museum.

When the animals revolt against the humans, they take over the entire farm.  There is soon a question regarding what to do with the farmhouse.  The farmhouse was where the people lived, obviously.  Now there are no people, and if any animal lives in the farmhouse that would put that animal above the others.  The animals want a more egalitarian society, in line with Old Major’s wishes.

Old Major is actually quite specific on the issue of living in a house.

No animal must ever live in a house, or sleep in a bed, or wear clothes, or drink alcohol, or smoke tobacco, or touch money, or engage in trade. All the habits of Man are evil. And, above all, no animal must ever tyrannise over his own kind. Weak or strong, clever or simple, we are all brothers. No animal must ever kill any other animal. All animals are equal. (Ch. 1)

Naturally the animals want to keep the farmhouse as a kind of monument.  It is a reminder of how the people lived and lorded over animals.  The animals make a rule that you can’t sleep in a bed or wear clothes.  They bury the meat that was in the house.  At first, it seems like the animals are going to keep to Old Major’s design.

A unanimous resolution was passed on the spot that the farmhouse should be preserved as a museum. All were agreed that no animal must ever live there. (Ch. 2)

However, soon the pigs begin taking more and more luxuries for themselves.  They tell the other animals that they are the farm’s brain trust, and they deserve things that other animals do not get.  It starts with milk and apples, but soon the pig-leaders are getting more and more human trappings.

 [The] pigs suddenly moved into the farmhouse and took up their residence there. Again the animals seemed to remember that a resolution against this had been passed in the early days, and again Squealer was able to convince them that this was not the case. It was absolutely necessary, he said, that the pigs, who were the brains of the farm, should have a quiet place to work in. (Ch. 6)

So much for the museum!  Soon the pigs are sleeping in beds, and even trading with Humans for alcohol!  The pigs take more and more control and begin to act very dictatorial after Snowball is run off.  Napoleon and his secret police of dogs ensures that there is no trouble among the animals, and the commandments are soon history.  The pigs are in charge.