Market
Once built, you will be able to choose how your gold will be distributed every 24 hours. You can choose between an 8 hr market or 24 hr market. The latter choice will spread the same amount of money every tic to your account whilst the 8 hour market will give the majority of your daily gold in those 8 hours (or 16 tics).
The base level market does not have any requirements.
To upgrade, you require 50k, 1st barrack, level 5, first headquarters and to be a clan member.