Officers are new to OGame. You do have to pay for them. Looks like the prices are: $3.99 USD for one month, or $9.99 for 3 months. I don’t know if you can hire multiple officers. From the interface in OGame, it looks like you can hire multiple officers (one of each). The cost of Officers, plus Commander would be in the neighborhood of $17 USD a month to play OGame. That is if you buy everything in 3 month increments.
Here is the text descriptions from OGame about Officers.
The fleet admiral is a experienced war veteran and skilled strategist. In the toughest combats, he is able to create an overview and contact with his subordinated admirals. A wise emperor can rely on his support in the fight, and add more slot fleets at the same time into combat.
Bonus: max. fleet slots +2
The Engineer is a specialist on energy management. In times of peace he increases the energy of all the colonies. In case of an attack, he ensures the supply of energy to the cannons, avoiding an eventual overload, which leads to a reduced amount of losses during the battle.
Bonus: Reduces the losses of the defense by half, +10% more energy
The geologist is a expert in astromineralogy and crystalography. He assists his teams in metallurgy and chemistry as he also takes care of the interplanetary communications optimizing the use and refining of the raw material along the empire.
Bonus: +10% mine production
The guild of the Technocrats is composed of genious scientists, and you will find them always over the border where all would blow up behind any technological logic. No normal humans will ever try to crack the code of a technocrat, and he inspires the researchers of the empire with his presence.
Bonus: +2 espionage level for probes, 25% less research time