I just replaced the master cylinder on mine. It was a pain trying to find the part. You should just go to a dealer and shell out the 400 bucks for it. It's single circuirt brake master cylinder, so if you go through PartsShop, you have to make it clear that they can only get it through a dealer, otherwise they might send you a dual circuit master cylinder like they did me.
I also wished to replace the clutch master, but not even the dealer could locate the right part. It's a pretty easy job though.
If it is in nice shape cosmetically, and nothing major is wrong with the engine or tranny, then I'd say that price is a steal!

Expect that the other fiddly bits might need work, like the shift linkage, brake booster or exhaust.
Also, ask them if they regularly greased the chassis. Theres about 20 zerks under the car that need greasing. I try to do it every oil change. Hopefully an owners manual comes with it, there's lots of things in there you need to know, like how to oil the distributor and that the manual transmission takes ATF.

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63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6