Construction companies must buy resources (cement and electricity) to be able to build. You can buy resources via The Exchange at market prices, or directly from other companies via the Private Trades system.
Construction of a retail store requires 2000 kWh electricity and 3000 kg of cement. Construction of an apartment building costs 20000 kWh electricity and 30000 kg cement for the first story, 40000 kWh electricity and 30000 kg cement for the second story, 60000 kWh electricity and 30000 kg cement for the third story and so on.
To start constructing the company must first receive a contract offer from a land owner. On the land page, the land owner can fill out a form to create a construction contract proposal. Once the proposal has been created, the construction company can view this proposal under the "Manage Construction" tab. A table will show the wanted construction, the resources needed to build it, and links to either accept or reject the offer.