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]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "upkeep":
   TLC, aid, backing, bread, care, carriage, carrying, conservancy,
   conservation, conservationism, daily bread, economic support,
   endowment, environmental conservation, expenditure,
   forest conservation, forest management, keep, keeping, livelihood,
   living, maintenance, manna, meat, moral support, mothering,
   nourishment, nurture, operating costs, operation, outlay, overhead,
   preserval, preservation, price support, protection, provision,
   psychological support, reliance, repair, running, safekeeping,
   salvage, salvation, saving, security blanket, soil conservation,
   stream conservation, subsidization, subsidy, subsistence,
   subvention, support, supportive relationship, supportive therapy,
   sustaining, sustainment, sustenance, sustentation,
   tender loving care, upholding, water conservation,
   wetlands conservation, wildlife conservation