Hiring a LOT of NPCs can be done by following this routine. 1- Go to the area you want to scout or operate in. 2- Take no more than 5 NPCs, one of these will be your scout and should be a Mighty Man, or an NPC with an ID under 1000. 3- Use the scout to see the NPCs inside of fiefs using the kidnap option. 4- Enter the tavern to the potential NPCs' fief
5> hire them away..
6> once hired and you reached to 20+ npcs..find an inactive fief to dump most
of them except the ones you need to do in operation..
7> do the operation..
8> repeat 1>
That's how you can siege, hire NPCs and resupply NPCs to your friends.
It will take about 30-60 minutes to move 90 days..so you can save real cash!