If you can cast Create Greater Undead, you should be able to get access to simulacrum and, since the simulacrum possesses the abilities of the creature you create but is eternally bound to you, this lets you start up your vampire chain that way. Simulacrum just costs 500 gp per half-HD you want (so 4K for a 4th level copy of the 8th level sample vampire sorcerer in the core bestiary), which is basically free for a 15th level character.
If you're a Cleric, Oracle, Sorcerer who for some reason failed to take this ridiculously powerful spell, or other 15th-level full caster unsure of what to do since the spell's not on your spelllist, take heart: there are lots of ways to get access to whatever spells you feel like at such high levels.
The easiest way, of course, is to get a Scroll of Simulacrum(vampire), which should cost about 10,275 gp for a 4th level copy of the sample vampire previously mentioned. Such scrolls work for anybody with a UMD skill, though, and only get you the one vampiric mind slave.
The easiest long-term way, for most characters, will be a Page of Spell Knowledge. That magic item costs 24,000 gp for a copy of Simulacrum and lets anyone who's a spontaneous caster (e.g. a Cleric, Oracle, Sorcerer, or Druid) and who either makes a DC 20 or 21 Use Magic Device check or has Simulacrum on their spell list cast that spell as if it were one of their spells known. For 'real' spontaneous casters like Oracles what that means is clear but for classes that have a "Spontaneous Casting" class feature, but are typically thought of for their prepared spells (like Clerics and Druids) it's less clear how that works, and from what I've seen you usually have to prepare the spell normally after learning it via the item, rather than being able to cast it like your spontaneous spells known.
If you're not a caster of any sort, you'll need to fall back on intelligent items for your mass-vampire-producing needs. That'll cost at least 183,000 gp for at-will simulacrum and the cheapest regular item power, but afterward all the simulacra you create (vampires or otherwise) are 100% free, requiring only 12 hours of someone else's time.