I have not followed this thread of discussion so forgive me if someone has
already mentioned this:  The National Trust for Historic Preservation has
compiled at least four such guidelines specifically geared to Historic
Districts that have lower income families or areas where the market value of
the houses cannot support regular and expensive maintenance, they are called
"affordable" neighborhoods.  The only project in the North East I know of
was for the Dwight Neighborhood in New Haven, CT

Best,
Leland