Hey! Same here! I find it a challenge as well, so I make sure my clients know up front that I shoot natural light, and that we will need window light if we are shooting indoors. I always try to shoot outside, but if it's pouring, and there isn't much light available I will generally reschedule. My new camera has helped me be able to shoot in lower light though, because I can up the ISO with minimal grain, so better equipment can give you more flexibility too :)