Well, what effect would this have on the campaign? If it doesn't have a real effect (it's a generic fantasy town, except that the local lord is the PC), then it could just be the SFX of his wealth and nobility perks. If he wants to build it as a base, then he gets whatever he chooses to pay for. If he wants followers based there that help him adventure (men at arms, a wizard that can scry) he can buy them as followers, but he shouldn't have to pay for the local guards if they stay in town while he's off slaying dragons or whatever.
And, of course, if the town is constantly being attacked by dragons, then it's a DNPC.