I think Fred did an excellent job of summing-up the facts, as one would expect from a true professional. Judging from threads I've read around the net, Garrard grease is truly infamous! And judging from what I've seen of Garrard TTs in the used-audio market here, the quality runs from the outstanding level of the sought-after 301s and 401s downhill to some very cheap and cheesy units. MOST Garrards are probably not worth getting, from an audiophile standpoint, but I'm not sure about the 50. In any case, expect the grease problems with most of them.
If you are looking for an idler-wheel turntable that is good value-for-money, try for a Dual 1219 or 1229. You'll still have to clean them up an re-lube them, which can take a few hours (like Fred said), but the grease won't be nearly as bad as the Garrard grease.
An even better idler-wheel turntable would be a Lenco L-75, or one of their other heavy-platter models. [I currently have five Duals and have passed up a bunch more, but I just recently got my first Lenco, only the second or third one I've seen for sale --not counting a belt drive one I found today. Lencos seem much rarer, at least here in Hong Kong. They are also sturdier and simpler, although the tonearms are a bit disappointing. ]
Alternatively, there are many decent belt drive TTs (like the Thorens Fred mentioned) and the late-seventies/eighties direct-drive tables from Japan, if you can find them where you live, are excellent (if often a bit expensive).
You might find this interesting. Not sure if I completely agree with the info, but it seems mostly accurate:
http://www.geocities.com/midimagic@sbcglobal.net/safchang.htm