I haven't owned a Volvo for very long but maybe I can help you a bit...
I think what Slowbrick said in regards to price is right. As an example, I bought a 92 240 sedan (auto) for $1750. Technically nothing needed doing to it - it came with RWC and was ready for use as a daily driver. I decided I could make it better though, just by giving it a decent service - filters, leads, distributor, etc. Wouldn't have cost me much more than $200 for all the parts. If you get a mechanic to do it obviously it will cost more. Basically though, 240s are pretty good cars so there is a good chance that you wouldn't actually have to get a complete overhaul of the mechanical stuff done, just a decent service.
If you get a high mileage car - I wouldn't let that bother you. It all depends on how the car's been looked after. Mine has 400,000 km on it and drives perfectly.
Also - where are you?
Here are some I've found on Gumtree:
http://www.gumtree.com.au/s-ad/banks/cars-vans-utes/1985-volvo-s40-sedan/1092045333
I have actually spoken to the owner of this one and if you're happy with the earlier (82-85) style front, K-jet and auto, then it would be a great car. Because it's an old car you'd probably need to get a couple of maintenance types things done but I'm pretty sure it'd serve you well. It was owned by an elderly man who owned it from new. Also has Virgo wheels which look nice.
http://www.gumtree.com.au/s-ad/currumbin-valley/cars-vans-utes/1988-volvo-2-sedan/1093305587
Another auto but it has the later styling, LH fuel injection and is pretty cheap. Doesn't look too bad.
http://www.gumtree.com.au/s-ad/mount-gambier/cars-vans-utes/eoi-volvo-240gl-/1093268156
A bit older, and would probably need a few hundred $ put into it, but it's a manual which is good (manuals are hard to find).
http://www.gumtree.com.au/s-ad/warrawong/cars-vans-utes/volvo-240-manual/1093184133
Another manual, but you'd probably want to reserve around $1000 to get it nice.
Has what I think is the best looking front end (bonnet/grille).
http://www.gumtree.com.au/s-ad/osborne/cars-vans-utes/volvo-240-gl-240/1093045537
Manual which is good, and I don't think you'd need to spend much. If you're happy with an older one, would be a good buy.