1920s house

Here's your typical (nicer example) 1920's San Francisco row house on sale:

http://www.redfin.com/CA/San-Francisco/131-Ellsworth-St-94110/home/764220

Lots in San Francisco are very rectangular (much longer than wide). 

This house has bay windows in the front (typically 3 windows like this, or four or five windows with barrel front):

 

The living room is typically up front, with the bay windows out front, brick fireplace (typically sandstone, but in this case has been painted over) with built in shelving on both sides, moulding on the ceiling:



Older homes normally do not have open floor plans (at a time when central heating was not common/nascent) to preserve the heat.  Typically, behind the living room would be french doors leading to the dining room:

 

On the other side of the house would be a kitchen and bathroom, and in some cases a nook.  On the back the house would typically be two bedrooms side by side.  In bigger homes there might be a third home upstairs.

 

Unlike newer homes, the first floor for homes built up to the 1950's in San Francisco was typically originally built as a wide open unfinished basement, with tandem garage.  Some wealthier houses might have a finished "social room" in the first floor with fireplace and bar.  Nowadays, most San Francisco homes like this will have developed the first floor to add livable rooms.  For most of these houses, it should be possible to add one or two rooms plus bedroom and still retain the tandem garage.  In other cases, one or both spaces may have been developed into living space to make the living space even larger.  Personally, I like to live in a house with room to park two cars indoors.