1.6 Zetec is the most common model made Nope 1.4 LX outsells all others in irish market. but there also some nasty ones starting to appear. No offence to moondance but the 1.4 is too underpowered, and the 1.8 is too heavy Same weight as 1.6 bar a few kilos. 2.0 is thirsty and the TDi and TDDi diesels are best avoided Older design engines, a bit noisier and less refined than later common rail TDCI units, but rugged and reliable.
If you are looking at a pre Nov01 (Indicator lights are on the front bumper) model then make sure the timing belt was changed and also the cambelt and pre-tensioner if you are keeping it a few years. ABS never really became available until Nov01 onwards too, but is not standard in this age range. I had a 1999 Focus with abs.
Check the steering wheel too for excessive wear in 1 spot if the car is under 50k miles. Could be clocked... I have had my focus for 3 years, put 50k on the clock and the wheel is only starting to show wear with 80k on it. Drives great too...
As with most cars in this class the suspension will be coming to the end of its life, exhaust could be prone to getting holy if it is pushed hard regularly, and also check the oil and coolant for evidence of cross contamination of the either oil or water, which would show evidence of a head gasket leak (again, only if the car has been pushed hard).