HO scale is about 1:87, almost twice as big as the N scale which ranges from 1:148-1:160. If you're looking for a mini house for your dollhouse N scale is the way to go. N gauge and N scale are often interchanged, but N scale can fluctuate sightly smaller whereas N gauge is 1:148 only. There are also Z scale at 1:220 and T scale is 1:450 if you want some super minis.
Here are some really cool houses mini2b found on ebay. These unique train set modern houses are being sold by the builder. The first was inspired by South Florida architecture and the second by Miami Beach Art Deco style. These can be found in beachboy350 ebay store.
Here are a few others that I found on ebay but had to pass on as they are too big for my collection. The "DETAILED FALLER NR220 FLATS HO" sold for around $33. The set of two Vollmer HO houses is currently up on ebay here. The house in the middle reminds me of the vintage Vero houses.
(images from ebay - top two are from beachboy350, Faller NR220 and two Vollmer houses)