I'm at work right now at downtime, so I'm just wondering, so when I'm home I'll be ready;

Do I talk to a guard for it to trigger a quest, or do I have to go to a certain capitol city in which then a courier will tell me how to create a house?

Also, are these areas where you cannot buy a house, for example, Markarth, Falkwreath, and Dawnstar?

they say a courier is supposed to give u a note that says ur able to buy land and adpt kids, but i never did..so i just went to dawnstar and i had the option to buy land avaible...kids now have adopt option but u have to have room for them