If I OFFER to take someone to Disney, then I just assume that I am covering the DVC Rooms and the cost of them. I only make those offers to family members who probably couldn't afford to go anyway, such as some of my children WITH my grandchildren.
If I am planning to go and stay somewhere and I have extra room, I will often tell family members about it and let them decide if they are interested in going. In such a case I don't 'charge' them, since I was going anyway, but if they OFFER to help pay the cost of the room, then that is nice. I let them do it. But even if they offer, if they don't come up with any money (this happens frequently) then I never mention it.
IF a family member or friend comes to me and asks if I have DVC points and could make them a reservation, then I generally tell them that I charge Family and Friends about half price. This is typically about $10 per point. I have, unfortunately, had a number of family members (and a few friends) who offered to pay for this, but then either didn't pay, or only paid SOME of the cost. That is fairly common. I have found that if I haven't received the money BEFORE their trip, then I never receive it. In such cases, I often consider it 'a gift' and I don't hound them for it, afterwards. I fact, I generally don't mention it at all, but I REMEMBER those times and if those people want to have me make reservations for them again in the future, then I MAKE SURE that they understand the cost, that I have FEES that I need to pay, that it isn't just FREE, and they need to make sure to pay me for whatever they are using.
Again, it is NEVER my plan to make money from family and friends, and, clearly, I most often LOSE money, but I think asking them to pay a reasonable amount, to cover Membership Fees and other expenses is a very reasonable thing to do. UNLESS it was my plan from the beginning to make it a gift.