When you build a building it's building cost is subtracted from your total money. After that it takes x turns to finish building that building. Thus all buildings take the same time to build.

In Civ 3 it should be changed before it can be implemented because requireing the total building cost up front isn't totally accurate. When you build a building you don't need all materials up front, but you do need some to start with, but you can buy everything up front if you want to.

In Civ terms buildings have a cost and only 20% needs to be paid up front and 10% per turn (for wonders, since they take forever to build anyway and cost a ton, 10% up front and 5% per turn). Just like in the previous Civs you can pay for the remainder at any time while it is being built.

As for a set number of turns, that's debatable though somewhat accurate since you can't force a worker to work faster, but if you put more workers to work to build it faster.
The way it could work is it takes x turns for one worker (don't aks me to define a 'worker', probably just one pop. point) to build it and if you put more workers to work on the structure then it would decrease the building time by 40% each added worker you select to work on that building (ie: 1 worker=100%, 2 workers=60%, 3 workers=36%, 4 workers=22%, etc. not divide by the number of workers since the more workers you get the more that don't do anything).

For those of you who don't want to worry about numbers just put 3-4 workers on each project for max output. Any more than that and you get bogged down by too many workers. (they could also complicate it by using some wacko formula so that if you get too many workers on one project than it goes slower than with less workers, more realism, not too much more complicated).

First, you need to be able to stockpile shields. That way you can build up a bank of resources in each city to spend on your build queue or save for a rainy day or load in trucks and move around if you need the shields elsewhere.

Second, you need more citizens in your cities and you need to be able to assign them production tasks. Taking SMAC as the current model, currently all of your citizens either work in the fields/mines/solar farms, on morale or on research. This is unrealistic as you don't have anyone working in your production centres. So what you need is to be able to assign workers to working on producing whatever is in your build queue as well as all those other tasks. More workers equals faster production, but it also means faster consumption of shields. So if you've got enough workers and shields you could build something in one turn (unlike now which only requires gold/credits, which is unrealistic).

To add another layer of complexity, you could have multiple build queues in a city and assign workers to each of them. The number of queues would be dictated by the number of workers you had available to assign.

Sigh, more things to balance.

If you use more sheilds then you have available then you start draining the stockpile. If there are no more sheilds in the stockpile and you are still using more sheilds than you have available then it brings up a message saying so and workers are 'laid off' untill the deficite is made up (if you have 10 workers working on a project, and each worker uses 1 sheild per turn, and you only generate 6 sheilds per turn, then 4 workers are laid off)

You cannot 'pay for' an entire building, but you can recruit workers from other nearby cities who are less efficient depending on the distance from their home city (if one worker uses 1 sheild per turn in the origonal city, then a worker from a nearby city would use 1 sheild, but would only put 3/4th's of a sheild into production. A worker from a further city would only put 1/2 of a sheild into production, etc.). If you have a worker from one city working in another city for an extended period of time, then population from that worker's home city migrate to the other city and the worker's efficiency increases.

If wages are included then wages are generated from trade. If the workers' wages aren't paid in full then their efficiency goes down until it is paid.