The previous two replies are very thorough and thoughtful, and the only thing I can add is that the grill area on the 1800 is very vulnerable to damage. If you contemplate parking the car on the street, you will probably have the grill bashed-in by some thoughtless oaf in an SUV who doesn't stop backing up until hitting something. Repairing this kind of damage can be very expensive as the chrome grill is costly to replace, and the front sheetmetal is all integral, and therefore has to be repaired in place or cut out and rewelded. None of the front sheetmetal is bolt-on except the hood.

I can verify the post about upgrading the handling with after-market parts. My 1800ES has stiffer springs, Bilstein shocks, ipd sway bars F+R and wider wheels and tires. It corners like a slot-car, and is a blast to drive on local streets as well as on the highway.

Hi Ryan,

dc isn't all that cold, but it does get snow sometimes. rust issues??

Most of the ones that were driven on salted roads no longer exist, and most that do exist don't get driven on salted roads. It's not a year-round car in such conditions.

cost of maintenance/repair. i don't have access to a garage and tools...expensive???

Parts are very reasonable and generally available. Mechanics that know the first thing about P1800s are extremely rare. It's a very simple car, but the technology is so old that most mech these days have no idea how it works. It takes a specialist. It's a great car for DIY with basic tools if you're willing to learn about it.

air conditioning. dc gets very hot and humid in the summer. is a/c an aftermarket thing or standard?

It was a dealer-installed option.

the p1800 isn't exactly known for its power. is this a problem generally for mostly city driving?

In stock form, it's a terrific highway cruiser that'll run 90 mph all day. It has adequate power for stop-go driving, but it comes alive over 45 mph.

dc has a lot of pot-holes. how is the ride in a p1800? how fragile or robust?

Designed for gravel roads in Sweden. Tough as an anvil.

anybody with experience regarding passing us emissions (post-1967) models only?

I never had trouble passing California emissions once I learned to fix and tune the car myself. See above about mechanics.

any common gremlins to look out for when purchasing?

1) Rust. 2) The mechanic(s) who last worked on it. 3) Modifications done by the previous owner.

If you can do your own work and you don't need to drive on salted roads, it's a perfectly viable daily driver. It all depends on the condition of the car, and of your willingness to take care of it. Once in good shape, it's not at all demanding -- very reliable and lasts just about forever. The car with the highest mileage in the world -- now over 2 million miles -- is a '66 1800S owned by Irv Gordon, who bought it new. The engine has been rebuilt exactly once; it's still running on the original block and head.

For $6000 you should get a very, very nice 1800 indeed. Not quite a flawless show winner/museum piece, but a very clean driver that looks good even up close. For that price, it should have no/never have had any rust. Rust is the main weakness of these cars - they are made of thick metal and it takes a while for the rust to get started, but they have a complex body structure with lots of dead end pockets and they will rust worse than your typical Volvo sedan of the same age. $6000 should put you out of the rusty cars, however. Consider buying a car from a sunny climate, like the southwest, where the car hasn't been exposed to moisture for decades.

Your list of concerns:
weather - if they salt the roads in the winter and you drive on them, your car will rust, period. I don't think its feasible to wash them well enough to get the brine out of the body cavities it works its way into.
cost of maint/repairs - mechanically it is identical to the common sedans of the same vintage. Parts are relatively easy to get, not very expensive. Its not a Alfa where you will wait for 6 months to get a $500 starter. However, B18/B20 parts seem to have made a retreat from local parts stores, so availability is mail order with a few days lead time in worst case.
air conditioning - some later model 1800's will have 'Volvo' A/C as installed new at the dealer. I have it in mine - it puts out a cool breeze on a hot day. It's not going to chill your bones, I guess the Swedes, working on the AC system in the middle of the winter, were probably a little skeptical of the capacity needed...
performance - the car is heavy and feels it from a stop. Its more fast than quick I'd say. A little slow to get going, particularly by modern car standards, but an effortless cruise when up to speed. Cornering with stock suspension and tires is laughable by modern standards - wider tires/wheels, IPD sways front and rear, and Bilstein shocks, possibly some progressive coils will make a dramatic improvement.
suspension - pretty bomb proof - solid and sturdy.
emissions - an E/ES model with fuel injection should have no problems, given a properly operating system. Troubleshooting the D-Jet Bosch system isn't too hard. Older carb engines will have a hard time being tuned if the carbs are worn, but the standards are pretty loose on cars that old. Basically if its in good tune it should pass.
gremlins - rust, rust, rust. Although for 6 grand you should have a drivetrain and interior in very good condition as well. Really, very few weaknesses other than the rust issue. Did I mention rust?

I've owned my 1800E since 1987, and owned another one for several years prior to that. At one point I thought of them as the pinnacle of vintage Volvoing, and they are nicer than 140 and 120 series cars. But then I got my PV544, and discovered what the REALLY fun old Volvo is! The 1800 feels heavy, the interior is an ergonomic nightmare, it can be a little claustrophobic with that high beltline and small greenhouse. The rear seats are worthless - even small kids won't fit back there. The trunk is very small unless you leave the spare at home. Mechanically the cars will most likely last forever given non-abusive treatment and good maintenance. They look neat, although they miss that sports car mark by a certain degree - a little more Karmann Ghia than Jag XKE. They won't be as fast as they look without lots of money spent, and if anyone ever hits you it will be practically impossible to have the body repaired acceptably. All in all very nice, I just like my PV a lot more.