We have a spare room in our house (2 actually - but one is a play room upstairs now that the 3 children are all in together). Our house is set up so that the whole family sleep upstairs where there is a full bathroom and downstairs there is a guest room and another full bathroom.
Last year we had a homeless man live with us for about 3 months. Luke and I still think it was the right thing to do, but we found it very difficult. He was a really lovely guy, but we didn't know him terribly well and were conscious of the need to protect our children. I thought a lot about the parable of the Good Samaritan and how fear isn't a good reason to leave someone in their need, so it was a good lesson in trusting God. I think it was really good for our kids, they still talk about Stephen and found it difficult when he up and left because he busted with his drinking and gambling. It was also a good chance to talk with them about addiction.
And today, a gorgeous young girl from night church has accepted our offer to stay with us while she is in between rentals. She's from England and would really love to move in with a family full-time, but we don't feel like we can offer her that. We want our spare room to be vacant often enough to meet different needs. But, she'll stay til she has somewhere else to go. I feel a bit nervous about it - my space, my time, the ease of walking around in my underwear first thing in the morning!, but again, I'll need to trust God with all of that. Luke and I will set our boundaries about being home with her - it would be very unusual for Luke to be with her on her own, but we'll make plans so that that doesn't happen. So life will be a bit more complicated for a time, but that's ok.
We have a great house, and it's all because Luke is a minister. We have space and so we want to share it. I think it's good for our kids, although for our eldest (who is much more introverted than me) I need to make sure she has opportunities to retreat. The other two love having people around as much as possible.
If you've got other examples you'd like to share, please leave a comment!