The Collaborative International Dictionary of English v.0.48:

Upkeep \Up"keep`\, n.
   1. The act of keeping up, or maintaining; maintenance of
      persons, organizations, or objects such as machinery, by
      providing a location, repairs, and consumable items when
      necessary. "Horse artillery . . . expensive in the
      upkeep." --Scribner's Mag.
      [Webster 1913 Suppl. +PJC]

            Small outlays for repairs or upkeep of buildings.
                                                  --A. R.
                                                  Colquhoun.
      [Webster 1913 Suppl.]

   2. the cost of providing upkeep[1].
      [PJC]

WordNet (r) 3.0 (2006):

upkeep
    n 1: activity involved in maintaining something in good working
         order; "he wrote the manual on car care" [syn: care,
         maintenance, upkeep]
    2: the act of sustaining life by food or providing a means of
       subsistence; "they were in want of sustenance"; "fishing was
       their main sustainment" [syn: sustenance, sustentation,
       sustainment, maintenance, upkeep]