Space Settlement refers to people going to orbit because they want to, on a long-term basis. The dividing line between it and Space Tourism is that for tourism the stays are short enough so that transportation costs dominate, whereas for settlement the stays are long enough that construction and maintenance costs dominate.
This page concerns residents who are telecommuters, retired, etc. For information on people going to space to serve other markets (such as space manufacturing), see the pages concerning those markets.
I haven't seen a lot of writing on the economics of settlements, but a good introduction which focuses on the technology of a large-scale human presence in space is "Colonies in space", P.E.R.M.A.N.E.N.T., Mark Prado. It includes links to additional web pages on the subject.