Hi Fred,
... starting with a small single antenna with both 2m and 70cm on it (i.e. Arrow or other) ...
I've found that an azimuth-only rotor with a fixed elevation of 20° or so works well enough for most of what I do with LEO satellites. I got my rotor from ebay for $20. It is a primitive setup - manual tracking. Much of the time I prefer using an Arrow antenna.
If you are looking for rotor projects there have been two designs published over the past year or so in the AMSAT Journal. Here is some information you can use to find out more about these:
The AMSAT store has the printed circuit board for WA8SME's WRAPS inexpensive, portable az-el rotor system. See http://store.amsat.org and look for the "WRAPS Tracker Circuit Board". There is also a link to the article by Mark, WA8SME.
Bob, KI4SBL, wrote an article about his homebrew az-el rotor system, "CNCTRK – A LinuxCNC Based Satellite Tracking System", for the AMSAT Journal. Bob has details of this project and the parts he sells along with a PDF of the article posted on his web site: http://ki4sbl.dodropin.org/CNCTRK/
-- 73 de JoAnne K9JKM k9jkm@amsat.org