I disagree with the previous posters. I always bring a suitcase full of underwear, lingerie, outfits, heels, etc; whatever I need for what I'm shooting that day.
I always make sure I have something for the model to wear (in the case that he/she doesn't, or I don't like what they brought) because I can't go through their entire wardrobe before the shoot, and my experience has taught me that I cannot rely on models to bring the type of clothing I want to use for a shoot on any given day. And I'm not about to waste my time and money because a model didn't have the right clothes for what I wanted to shoot.
Sanitation is never a problem because I always let them keep the underwear once they've worn it. Something like pants or a skirt that I know I'll probably use again, I'll wash and hold onto it. Everything else I usually let the model keep. I don't give my shoes away as those are too expensive to replace every shoot.
This is how I do it... it works for me and has saved me many a shoots where a model showed up without the right type of clothes.