Get a Rolleiflex and the Rolleinar closeup lenses (Rolleinar 3 gives the tightest closeup).
Or maybe a Rolleicord or Yashica first, to experiment with macro in the TLR form factor and decide whether a separate SLR is necessary. I think it really depends on shooting style---once on, the Rolleinaer sets are trivial to use, but if you switch back and forth between macro and other shots frequently, it could get kind of annoying to have to keep popping two auxiliary lenses on and off.
San Diego, CA, USA
The lady of the house has to be a pretty swell sort of person to put up with the annoyance of a photographer.
-The Little Technical Library, _Developing, Printing, And Enlarging_