All the arguments against you getting that Merc are all totally logical, but I don't think you're thinking logically about this and if you have the cash - why not?!!
The car looks fine and you'll probably have a lot of fun with it should you get it - my only experience of this sort of motoring is through a friend and my sister - the friend is in the UK and owns a Bristol and my sister had a Merc 300SLC (aka the Bobby Ewing car) for a couple of years in London.
Both cars were (to an extent) cossetted problem children. The Bristol is a motorway stormer but also likes hard-shoulders. Parts are relatively cheap and my friend can do a lot of things himself and with the assistance of a sympathetic mechanic, but it's always (looks fabulous while) in the garage for something.
The Merc was an 88 model and was absolutely unmarked when bought. Normally people shrug their shoulders if they get a few dinges in a car that age, but the bill to get the front radiator and bumper replaced after a supermarket carpark knock by an unidentified driver had to go through the insurance because it was so eye-wateringly expensive.
The need for a family car caused her to change the Merc. She didn't lose a lot of money when trading it in, but it wasn't unmarked any more and the repairs that had been carried out were v.v.expensive. Overall, it was a costly exercise.
Both of the above cars drank petrol like it was going out of fashion and the insurance was also not the cheapest.
If you can afford it, go for it. I think you might find that its not as cheap an exercise as it looks.