Some guilds - as well as some noble houses - are in the business of providing mercenaries. In the context of the mercenary rules, mercenaries don't just represent soldiers; any major civil or military asset that is for hire to PC and NPC estate owners are covered by the mercenary rules, so that one might have mercenary Muster companies, mercenary Charioteer transport flitters, mercenary combat Engineers and the like.
In general, the guild or entity controlling the mercenaries pays up front to maintain the mercenaries on world - this is the 'expense' of maintaining a mercenary unit. Typically, if the unit is something that can get 'odd jobs' like infantry, jeeps, transport flitters or the like the 'expense' is about half of the total cost of the unit, to represent the soldiers getting odd jobs when they aren't on contract. If the unit is instead purely military like tanks, combat aircraft, artillery and the like the controlling group pays the full cost for the unit they maintain.
Mercenaries, of course, are a for-profit enterprise - and when mercenaries are employed under contract, their controlling organization sees a profit. Thus, a mercenary unit might be written as:
MUSTER MERCENARY UNITS "Bulldogs" Hoplite Company (2500/1000)
The Bulldogs, a heavy infantry company, costs 2500 to maintain when not under contract but makes a profit of 1000 when under contract.
Contracts or Single Jobs
A unit can make money in one of two ways - either by being under a formal contract to an employer, where they serve as full-time soldiers for the employer, or by negotiating off-contract 'single jobs' on a cash basis. Contract work is handled through business and fief reports; if a mercenary unit is under contract, the person paying either has a straight cash expense for the ordinary cost of maintaining such a unit (5000 fb, in the case of a rifle company) or, usually, increased conscription for the amount required to raise a unit of that sort. The owner of the unit's econ report than changes so that instead of the unit being Off-Contract and an expense (2500 fb, in the case of the rifle company above) they are On-Contract and earn a profit (1000 fb for our rifle company example.)
It is possible instead for the commander of a mercenary unit to not place the unit under contract and instead pay the out-of-contract expense, instead seeking to earn a profit by contracting out single jobs and the like for cash payments. This can potentially be very lucrative - it costs a noble 5000 fb a year to maintain a rifle company, for instance, so if a mercenary commander could find a year's worth of cash jobs he would make 2500 firebirds in profit (5000 fb, minus the 2500 firebirds it costs to maintain a unit) rather than the 1000 he would make if under contract. However, out-of-contract expenses have to be paid in cash by the contracting employer; if the employer has a fief, he cannot raise Conscription to generate cash to pay for single-jobbing Muster. This is because Conscription represents not just cash money used to support a unit but room, board and the like, which does not cleanly translate into firebirds in the mercenary commander's pocket.
If a mercenary unit is under contract to an employer, the commander can still negotiate single jobs for the unit, but it is wise to seek the permission of the employer first, as a contracted mercenary unit is expected to be standing regular duties like any other.
This is a sample table of costs for mercenary units. As a general rule, costs are figured off the cost to maintain a unit for personal use. If the unit can take off-camera 'odd jobs' when not employed by a PC or on-camera NPC, the out-of-contract maintenance is 50% of the normal maintenance. Muster riflemen, for instance, are assumed to be taking short jobs guarding merchant caravans and the like when they are not on contract, and thus make up a portion of their costs by doing so. If, however, a unit can't really take odd jobs the maintenance is the full cost of the unit - tanks, for instance, or fighter planes really are only useful in war and thus there is no 'off-camera market' for them outside of PCs or on-camera NPCs.
The table here has four entries - the unit type, the expense for a commander to maintain while out-of-contract, the profit while in-contract, and then the firebird cost to an employer to contract a unit of this type.
INFANTRY EXPENSE PROFIT COST Armsmen Company 500 fb/yr 500 fb/yr 1000 fb/yr Rifle Company 2500 fb/yr 1000 fb/yr 5000 fb/yr Ranger Platoon 1500 fb/yr 750 fb/yr 3000 fb/yr Commando Squad 3000 fb/yr 750 fb/yr 3000 fb/yr ARTILLERY EXPENSE PROFIT COST TL4 Battery 1500 fb/yr 500 fb/yr 1500 fb/yr TL5 Battery 2000 fb/yr 500 fb/yr 2000 fb/yr ARMOR/VEHICLES EXPENSE PROFIT COST Transport Company (10-15 Trucks) 1250 fb/yr 500 fb/yr 2500 fb/yr Mechanized Rifle Company 3000 fb/yr 1000 fb/yr 6000 fb/yr Armor Platoon 2000 fb/yr 500 fb/yr 2000 fb/yr Mega-Tank 1500 fb/yr 250 fb/yr 1500 fb/yr AEROSPACE EXPENSE PROFIT COST TL4 Combat Flight (2-4 aircraft) 2000 fb/yr 500 fb/yr 2000 fb/yr TL5 Combat Flight (2-4 aircraft) 3000 fb/yr 500 fb/yr 3000 fb/yr TL6 Combat Flight (2-4 spacecraft) 4000 fb/yr 750 fb/yr 4000 fb/yr Hopper Flight (2-4 hoppers) 1000 fb/yr 500 fb/yr 2000 fb/yr Shuttle Flight (2-4 cargo shuttles) 2000 fb/yr 750 fb/yr 4000 fb/yr Explorer/Star Yacht 2000 fb/yr 500 fb/yr 4000 fb/yr Gunboat 4000 fb/yr 750 fb/yr 4000 fb/yr Raider/Escort Sloop/Corvette 5000 fb/yr 1000 fb/yr 5000 fb/yr Frigate 8000 fb/yr 1000 fb/yr 8000 fb/yr