1994 Honda Civic Leaky valve, should I buy?

I am thinking of buying a Honda civic Dx coupe. The buyer states the compressor works, can be recharged but there is a leaky valve in the system so it leaks very quickly. How much will it cost to repair a problem like that? Should I buy and fix it? Their asking price is $1800.

HERE IS THE POSTING:

1994 Honda Civic DX Coupe, black with black interior.
1.6L 4-cylinder, 4-speed automatic
179,000 miles
Mechanically excellent, cosmetically fair.
Power steering/brakes, dual airbags, delay wipers, rear defrost, tilt
steering

35 MPG.
Runs very well, transmission shifts firmly as it did when it was new.
Two owner car
Non-smoker (always)
No pets in car (always)
Garaged year-round for last 5 years.
Full service history available dating back 8+ years
Newer tires
New brakes
Newer suspension bushings
Timing belt and water pump replaced at 90K and again at 170K
3,000 mile oil changes always. Uses no oil, does not smoke.
Regular transmission services, shifts as it should.
Newer exhaust
Very clean interior, glass is also in good shape.
Has a 1" receiver hitch, suitable for bike rack or lightweight
trailer. We used it for bikes.
AC compressor works, but system has a leaky valve. Inexpensive fix--
works when charged, but leaks quickly.
Paint is faded, some rust around rear wheel wells--car was garaged,
but it's still a Honda in this respect.




Thanks in advance, I don't know much about cars, this will be my first car, thanks guys and gals :-)