How do you make 3d models of houses?

I am currently developing a zombie survival game (not another one XD), and I was having loads of fun sculpting terrain when I realised that there was a dire need of towns on this not so glorious terrain. I am wondering where I can find 3d models of buildings (with interiors), or if anybody can point me towards some tutorials on how to make houses in a 3d modelling program. (Preferably Blender.)

Thanks in advance.

~Extraordinari Nobodi~