Top-level fighters (Lords and above) who build castles are considered "Barons", and as such they may invest in their holdings in order to increase their income.-OD&D, Men & Magic Vol I
When Clerics reach the top level (Patriarch) they may opt to build their own stronghold, and when doing so receive help from "above".-OD&D, Men & Magic Vol I
Charisma is a combination of appearance, personality, and so forth. Its primary function is to determine how many hirelings of unusual nature a character can attract.-OD&D, Men & Magic Vol I
In one of my Swords & Wizardry campaign the characters have reached name level, i.e. 9th level. Ashling Anubis , a 9th level Montebank (Thief-MU), Eoleandar , a 9th level Fighter, and Syrivald, a 9th level Thothian Mage (Magic-user with extra abilities). My refereeing style has always put a premium on the players interacting with the Majestic Wilderlands and one of the rewards is gaining allies and followers.
With Swords & Wizardry, (a OD&D retro clone) this is baked into the rules with the idea that at name level and with high charisma you attract loyal followers. During the course of the campaign I kept notes on who could be these followers for each of the three.
Ashling's followers were first encountered in the very first session of the campaign last spring. And it was not a auspicious beginning. The party ran a foul of the Madmen. The Madmen are the local thieves guild of Gormmah (a port city to the east of Viridistan on the shores of the Trident Gulf). Anubis thought he had something valuable to sell to them and the head of the Madmen, the Warden, laughed in his face. When the situation became hostile, Ashling casted his lone spell, Sleep, and hot tailed out of there.
Several months later in game time and real time, the party finally makes it back to Gormmah. There Ashling decides that a little payback is in order. Armed with a lot more spells he makes it way back into the basilica which served as the Madmen headquarters. Roleplaying his way in along with a few sleep spells he was able to sneak into the Warden's bedroom. The Warden was sleeping with a woman and so Ashling woke him up with a surprise! He used polymorph others to turn the woman into a squid and used his magical trident (which commanded sea-creatures) to order her to attack the Warden. In the ensuing confrontation, the Warden paid the 150 silver that he owed Anubis and the polymorphed women asphyxiated and died from a lack of water.
Then a few levels higher the party found themselves back in Gormmah again. By this time they acquired a ruined hill fort in the wilderness north of Gormmah and decided they needed a presence in Gormmah in order to supply the settlement they were building there. Ashling paid another visit to the Madmen and found the Warden had gone insane becoming totally paranoid in the wake of the previous encounter.
Ashling had enough of this and attempted to take out the Warden with the intent of seizing control of the Madmen. At first the Warden and his flunkies were no match despite fortifying the basilica. But apparently the Warden's madness was not simple paranoia, he make a pact with the demon. When he went down, he transformed into a hideous demon! After an intense couple of rounds the party destroyed the demon.
In the aftermath, Ashling became the new Warden of the Madmen and won his name level followers.