Or maybe you mean you can buy yourself a house like in Oblivion?
Offcourse, this is RPG but you can take it as action/adventure game also.
Well you can do it in any "freelance" game today, if not the "right way" (e.g. buying it) then by modding the game (it's very easy to build yourself a house in Morrowind for example using TES construction set, I know people done it in Freelancer too)
I guess you talk about something like that 'cause I can't figure out any other reason to have "permenant base of operations" than as a place to keep your items and have a place for your character to rest (restore health)
EDIT: I just saw that you mention RPGs in title, so the answer is yes: as far as I know you can do it in Oblivion, Morrowind (extremely easy to mod and bunch of house mods to download), and Freelancer but it's not
really an RPG and, as far as I know, you'll have to mod it yourself and it's (unfortantly) pretty hard if you never made a mod before.
None of those are on abandonia 'cause those are new games but those are truly great games and you won't be sorry if you get them (if you haven't allready)
