You can see the cheapo I built in the building/remodeling thread. It was a chore but I really wanted a house even the poorest Sim could afford. Like Twinmum, I place my furniture on the ground and then build the walls around the furniture, room by room. In 3 you could have a bathroom that was 2x2 with just a shower and jon and the sink being the one in the kitchen. In four you absolutely have to have it bigger because of the doors, so minimum 2x3. So that's one square of wall more expensive. I tend to build my kitchens pretty much the same shape, going for a U shape work area. That sort of automatically helps me place at least one window and usually the small table and chairs, (no more than 2 for economy) will fit nicely within that space with enough room for Sims to walk around and sit. This time I started with a kitchen, then added the bathroom, then the bedroom and tacked a small living room in front of the bedroom. When I was done it was a little more than $9K in cost including the 40x30 lot. It's tight, but cozy, and easily upgraded. Start with a standard box or rectangle, or even L shape and go from there. You don't make it pretty if you want it cheap. You add all the niceties later, like towel bars and paper holders and mirrors over dressers and curtains and all the chotchkes you want.
