Since so many quests REQUIRE buffs, there should be an npc cleric that buffs for a fee like the Grumbar guys used to in the underdark.
Magic weapon is a requirement for too many quests, so is protection from alignment, so these spells should be included and should cost about 75 gold each and have a long duration.
I like the idea of tradeoffs as well : say an evil npc cleric will cast magic weapon for you but as this gift comes from Beshaba you'll lose a point of str for the spell's duration.
There's one of these NPCs already, but unfortunately not near any quests that I know of.