One of the nice things about having a scan tool is that with many of them you can see if all the monitors have been run. I'll never buy another used car without plugging in to see if all the monitors have been run without triggering any trouble codes. Otherwise, you are in your very situation.
Now, that is not the end of the world, because the "check engine" light should really be called the "check emissions systems" light, because that is what it was created for origninally. The EPA found that a lot of cars were polluting because of problems with the emissions systems on the car, and owners had little incentive to spend money on the problem. So, they devised this light to freak people out and make them think they had a big problem that they had to go get fixed right away. It works.
Now, I would buy a scan tool. You don't need a fancy one, just something that can read the codes and clear codes. Then you can see what codes are being thrown. A lot of codes are easy problems to fix and don't necessarily cost a lot of money, O2 sensors, loose gas caps, etc.
All these older cars need a lot of maintenance, and the focus is a great car to learn on. Parts are plentiful and modestly priced. If you have to take it to a mechanic for every little thing then it is going to spend a fair amount of time in the shop. But if you have some modest mechanical ability you can learn to do many things yourself.
Focus Fanatics has been extremely helpful to me and I've learned to tackle a lot of jobs that I never did before. The more you do the more confidence you gain to tackle bigger jobs. It is a virtuous cycle and very rewarding.
Get a scan tool, (around $50), pull the codes and tell us what you've got.