For portrait and fashion modeling photography you're going to want a fast lens. so look for a f1.8 or f2.8 lens. And a 55-100mm would work good. But for portraits, because you are working with someone moving and what now. you want the fastest lens you can get for sharp pictures.
I've got a 18-55mm f3.5-f5.6 and I have a very hard time with getting a fast enough shutter speed under poor lights with a model. I like to use natural lighting.... but still. lol.