What does KBB and NADA say? Without looking, Im thinking 1200-1400 range if you are in the south or west, less if you are in the north.
You can almost always negotiate. Don't ever ask. Presume it. Make an offer, don't meekly ask if they will take $50 less.
What I would do on the phone is say its a little out my range so what would the absolute least they could take for it. Then, when they gave me a figure, I know that was the most I would have to pay. And I usually got them down even more in person when I waived hundreds.
personally for a 14 year old car especially a ford its a ripoff. 100k miles isn't too bad but you should get a car fax. the trade in value is in the 700s- to 1k. so your getting ripped off.
Everything is negotiable. VERIFY the miles, do not trust anything the seller tells you. Have the car inspected by a certified tech and run a VIN check report like AutoCheck or CarFax.
The Focus is a mediocre car at best before the 2005 model year. The 2004 came with any of three engines: a 2.0L SOHC, 2.0L DOHC, and a 2.3L. The 2.3 uses a timing chain but the 2.0s use a timing belt, which I would bet is overdue for replacement. At 14 years it should be ready for the second replacement and I bet it has not had the first, considering the relatively low miles.
Always have any used car inspected by your mechanic before committing to it. It costs roughly $100 and can (often does) save you thousands. If the engine is the 2.3L timing belt is not an issue. Otherwise, if the timing belt has been replaced - documentation is required - in the last five years and everything else checks out the car is worth $800-$1000 US. If the timing belt has not been replaced in the last five years it is not worth buying at any price.
I have no idea if you would be able to negotiate. Offer 15
You always barter when buying a used vehicle.
Knock down the price if it needs tires, brakes, or hasn't had a timing belt replaced yet.