You did commit the cardinal sins of viewing a car in the dark and buying the first one you saw, but I guess you're not expecting miracles at that price, so all is good!
It is possible to get them very tidy (and reliable!), but only if you put time and money into them. I'm not sure I would bother taking the arches and sills off straight away unless you have cause to - you can feel under the rear arch lips to give you a good idea of whether it is rusting or not. Same with the sills - have a look along the top of the sill, and feel the bottom of it under the car (plus it's very easy to break the side skirt clips). If all is good, then a proper full inspection can wait until the weather improves.
Even as it stands though, it should be a good car, and will keep you and your wallet busy for many months...