I tend to design boxes, so I make simsified versions of real house plans from real architects. There are a lot of modern ones out there on the net, but what I usually use are historic plans, since I love older houses. I use both http://www.antiquehome.org/House-Plans/ and http://www.searsarchives.com/homes/ a good bit.

@Dagwon
Are any of the houses designed by Polly available for download somewhere?

I don't know, sorry! They sure are cute, aren't they?

To the OP: As long as your sims can get places (think two wide hallways and use the "modular stairs" not the ones that place as an entire stair at once...) and you have all the items that you want them to have (Food source, bathroom, bed, couple of fun things!) it really doesn't matter how ugly their houses are. Mine lived in boxes for *years* before I started trying to make their houses cute! So don't be afraid to make a few ugly houses. I think we all do, at first.

@PanAm103 They were available on the Exchange, but I don't know if anyone saved them.

@Dagwon I am too embarrassed to fully describe the houses I built originally, but let's just say that the very first one I ever built had a 3x6 bathroom that contained only a toilet, a sink, and a tub. Also, it was brown. And you were required to walk through it to get to the bedroom. My sims didn't care.

Thanks again everyone for the links, especially the tutorial ones. I really appreciate those a lot! They gave me some really good advice on things to try.