I pulled 3 years out of thin air, certainly.

I'm sure you're right
about the time being much shorter than that.
The other point I would make to Cheryl--once you start computerizing
information, you want it to do more and more. Even if you are just
tracking all the owners who bring their pets to you, and which pets each
owner has, at some point someone will say "hey, can't the computer tell
us exactly how many dogs and how many cats have been seen by our
practice?" A properly set up database will let you run a search that
lists all the cats in the client database in seconds. God only knows how
difficult this would be in a list of addresses maintained in Word.
Furthermore, if you hire someone once to build you a custom database in
FileMaker Pro, any database expert can likely come along in 5 years and
improve it for you. If you jury-rig something in Word, no one in 5
years will remember what was done or how to improve it and it will all
need to be done again.