Tough, long lasting, cheap and not pretty. But enough about me.

I'm guessing by your use of the word 'estate' that you are UK based.
If so, 1,000 ukp will get you one in top condition; 500 ukp is common
for a decent one.

You won't get one that is completely fault free at that age, but make
sure that the engine is not making any untoward knocking noises (a
little valve clatter is OK), and that it doesn't smoke from the
exhaust under any throttle conditions. Have a look in the coolant
header - you don't want to see any scummy oil floating on the top of
the water. If it's an automatic, pull the gearbox dipstick - the oil
should be red; if it is brown, or smells burnt, the gearbox is almost
certainly near death. Make sure the transmission isn't audibly whining
(except in reverse).

With care (especially regular oil changes) the engines will last a
very long time. 200k is usual, and 500k not infrequent, though the
transmission may not be able to match the latter. Camshaft timing belt
needs repalcing every 50k miles, and it would be a good plan to change
this, along with its tensioner, and do an oil, filters and plugs
change as soon as you get the car. Have a look at the brake pads and
disks, too.

UK spec'ed cars of this age are mechanically simple, without any
engine management computers or exhaust catalysts. They use Bosch
K-Jetronic fuel injection, which is a mechnical system and very
durable, though not without its quirks.

The 700 series is not as prone to rust as the 200 series, but mine has
suffered a little under the load area. Climb underneath and have a
good poke around. Rear springs can get a little weak with age, but it
is not a major job to replace them.

Volvo spares can be expensive, but in the UK there are a couple of
specialist aftermarket suppliers (Eurocar Parts and German Swedish &
French) who have many counter outlets and do mail order as well. Get
hold of their catalogues.

Load carrying capacity is superb, comfort is good, economy is not
brilliant (+/- 23 mpg), but they are a fairly easy conversion to LPG
if you are interested.

There are plenty of these cars around at that age, so if you are not
sure of anything, leave it and find another one.

It's your lucky day, I've just bought an 850 and have a 740 for sale at a
negotiable price if you're interested. I don't want to get rid but it's all
extra expense. It's a 2 litre 1988 estate. Looks nice and drives well.
Beware the volvo v engines, this one's a straight 4 fuel injected.It's in
good condition and been well maintained. If you want to speak further,
please let me know.

These are for the most part solid, dependable cars. I don't know if they
were offered with the ZF transmission, but I would advise you avoid that. It
can be identified by having P-N-1-2-3-D and no OD lockout button on the side
of the shifter. The AW-70 and 71 are much more robust and abuse tolerant.