What's required for to build a keep?

[Saracen]

I D/L the "patch" and over wrote the files in the proper directory. Will this have an impact on a saved game? What is required to build a Stables by the way. I never see one be built but it is required to build some units. Yet I seem to be able to build all the normal horse units? Another mystery to me, LOL!

I can build Egyptian and Phoenecian warships. Egyptian costs 3 times as much and twice as long to build but has worse stats???? What am I missing here?

I am building units and structures in a dozen provinces every turn. I am still gaining 10,000 to 15,000 bucks a turn. I did do the patch. Any thoughts?