I use a 1979 Volvo 245 as my daily driver! I paid £1000 for it; which seems extreme, but it was a 2 owner car with 60K miles and absolutely no rust- none. Since then, I've replaced the cambelt, entire cooling system, and had the automatic gearbox rebuilt. (my fault for carrying too many paving slabs up a 1:3 hill.) Also, the gearbox guru I took it to said my gearbox had been done previously and the torque converter was just drilled, flushed, and painted black!
The other repairs were just age related.
I now have for about £2000 a car that will likely last 30 more years, I can drive across europe in, and rely on for work everyday.
I highly reccomend 200 volvos- and my advice is to look for a 2.1 litre carb engine. These use a stromburg carb thats much better than the solex used on later cars and are easier to fix than injected/ computerised models.
The 2.1 (B21) engine is a non-interferance design, so if the cambelt does break, it won't do any damage. Its also the most bulletproof of the engines, although they're all robust. In the mid-80s, they redesigned the engine to make it more efficient and removed some of the over-engineering of the crankshaft etc.
The 3 speed auto is a BW35, which is pretty good, as its an old american design and was used in nearly every automatic RWD car from the 60s and 70s over here. It does kill the fuel economy though.
4 speed or overdrive gearboxes are brilliant if you can find them.
I love working on it- you can remove the whole front grille/ panels and headlamps in minutes, and can literally stand in the engine bay.
Saloons are very cheap, as everyone wants the estates- definately consider if you really need the extra space. They also seem to usually be bought by old men and are better maintained.
Rust isn't really an issue- just check the windscreen doesn't leak.
Electrics can be dodgy- and I've found its nearly always a loose fuse. The fuseboard is poorly designed, and the springs don't hold the fuses well. A leaking windscreen can make this worse.
You can pick up a nice one for £500-1500. BUT regardless, budget on another £500 or so to replace the cooling system, all rubber hoses, suspension bushes, brake pads, carb needle/ diaphragm whether it needs it or not.
High mileage is not a problem, and I think alot of the problems I have had were due to my car not being used for a while.
Year wise, everyone has their own views, but I think '78-84 are the best, as they have better steel than those from the mid-70s but don't have the gadgetry or interferance engines of the later models.
Always use only volvo oil filters- they have a one-way valve to prevent engine wear on start up. Only use red antifreeze.
BW35's take Type F oil, but if its been rebuilt, you can use Dexron2.
A saloon with LPG has to be the most cost effective motoring if you're looking at long term ownership.
Hope someone finds this interesting!