[OOC: You need to outfit him with a horse of some description (?1 for a rouncy - you could get away with a sumpter for 100d, 16d for tack and harness), a set of armour (15d), and weapons (about 50d). It also costs ~?1 per year to maintain a squire.
Keep in mind a squire's horse is effectively your spare in battle, and the squires weapons are your spares in battle. The better equipped your squire is, the more use he will be to you. If you equip a squire with a charger, a sword and half a dozen spears, those resources become available to you in the event you are unhorsed, or lose your weapons.
Typical chores that all squires must perform include tending horses, sharpening weapons, polishing armour, helping don armour, carrying messages, preparing and handing over fresh weapons, providing the knight with a horse, taking charge of prisoners on a battlefield, riding errands, standing guard, waiting on the knight at a banquet, rescuing and carrying off a wounded knight from the battlefield, and fighting when so ordered.