My opinion is, that you install a actual debian system for "work-related" things, if you have such things. I think this makes sense for security reasons. You can install some old operation systems along debian, thats no problem. If your 486 has PCI, throw in a Promise IDE controller.
From them you could boot cdroms and install harddisks up to 2000 Gigabytes (if I remember the manual correctly, this is no fault from me the size is correct). RAM is always important, but as I remember a Debian 5.0 "Lenny" installs with 32 Megabytes. For a text system, of course. You may throw in a "fancy" graphics card, that you could use some higher framebuffer resolutions. 1024x768 in framebuffer compared to the gerneric 80x25 is very comfortable.
If you install 64 Megabytes or more, you could try some X oriented things. Fluxbox or Openbox for example. They are quite lightweight. LXDE is also an opinion (and only the deskop system!), it uses Openbox and gives you a Windows like menu feeling. I made some tests with lenny and a Pentium 166 some time ago, to get the specific RAM requirement, and the summary is, that, even with 64 Megabytes, the system is quite "usable" as long you do not run some "heavy" applications like firefox or openoffice.