Stephanie, now that you are hoping to purchase the Luna Pro F (or Profisix) something to look out for which may or may not be useful, as Helen pointed out.
I've had a Profisix for 21 years and over time I've accumulated the odd accessory or three.
Probably the cheapest secondhand accessory and very useful in the darkroom, is the Lab attachment. It pops on the end of your meter, and gives you some possibilities.
The most useful possibility is the ability to take a reading, move the enlarger head up or down, take another reading to get your new enlarging time, or move the aperture on the enlarging lens to null the meter to get correct exposure with the existing time. Very useful in a minimal equipment environment, where one piece of base equipment can be used (with little extra cost) to do another job that normally requires something that costs more than a handful of dollars. I paid $10 for mine about 18 years ago.
The same Lab accessory, also allows you to work out the contrast grade of paper that the negative requires. This is useful in ones early days in a darkroom, I find this feature not a requirement for me these days.
If ever you go to LF you can get the Profi-flex attachment, this turns your meter into a TTL meter on any ground glass screen, wonderful for measuring light falloff when trying some interesting bellows and/or rise and fall things.
I mention these as interesting and usually extremely cheap accessories, which can enhance your meters worth.
I have managed over the last 20 years, to pick up 5 of the 10 accessory items, for just under $200 AUD, which is about $140 US.
The Profisix by the way, is the heart of the Profi System, in the same manner that a camera body, is the heart of it's system!
Mick.