I had a 240 as my first car, and although I spent a ton of time doing stuff on it (even just maintenance) I did learn a lot at the same time. I would say that it's a good choice as long as you're prepared for all your friends to ask why you bought an old Volvo!
Just bear in mind that while 240's are very solid cars they are not at all safe compared to even basic modern cars. However they have good brakes, great visibility and if you're prepared to spend a bit of $ you can make it handle pretty nicely, and while this means you might be less likely to get into a sticky situation, the lack of ABS etc is a let down.
If you do decide to buy it, bear in mind that it's an old car and it WILL have issues, many of which Spac has mentioned. I would also add a couple of things like be prepared to be hunting for good interior trim pieces, and the clips for both interior and exterior trims are often going to break as soon as you touch them.
Mechanically they are very robust as you probably know. While they are simple cars to work on, I found simple tasks often frustrating, eg the oil filter is located under the exhaust manifold, above an engine mount and with the steering rack in your way, so it's a pain to change it without getting oil everywhere, especially compared to almost any newer Volvo. Also due to the age of the car, you will often find bolts reluctant to come out, etc etc. However it's a good learning curve.
That wagon you're looking at looks super neat though, and being a late model manual it is one of the most desirable 240's you can get, although it's probably a little bit overpriced.
