I did this for 9 months when we sold a house quickly and were waiting to move towns. I love my inlaws and it was better than all the years I had to live with my parents as a kid but father in law very stuck in his ways and drove me around the bend. I just kept reminding myself they were good enough to take us in, kids, dogs and all.
Please don't. Not if you want to keep your marriage and your sanity. My SIL lives with us. Was supposed to be until she got on her feet. We are pushing almost 2 years. My husband and SIL act like they did when they were kids and I feel like the mother. OMG, please don't.
I took GREAT advice from those on TAM and am trying to find her a place myself. Got a good tip today.