Hello there!  Well, not five seconds ago, my brother asked me a 
question that led to this idea.

Would Nabiki charge Ranma for sex?

	Going by the source it's obvious that Ranma has very little desire for 
sex, If he had any desire he has several free sources to choose from.  Also from 
Nabiki's dating storyline it seems that she tends to date guy's to get them to 
spend money on her then dumps them so she doesn't seem to have the desire for 
sex, or the need to resort to it.
	Of course that leaves the possibility for character/situation 
modification in fanfict's open, but that's obviously a straight question of 
Author's choice.