When we decided to do this, we knew we were going to borrow some undetermined amount of money to supplement the proceeds we had from the sale of our apartment. We didn't know exactly how much or when we would need it. A year ago credit was still VERY easy to come by, even for someone like me who hasn't had a regular W2 for awhile. We have some other assets and very good credit, and so when I called around and talked to some mortgage brokers I was satisfied that we'd have no problem.
Fast forward to the late spring, when it's time to actually borrow the money, and things were getting much tighter. If I'd waited another couple of weeks we might have really been in a pickle. It worked out fine in the end, but nobody's lending me another penny for awhile. So if we get really desperate we can always try this - a genius plan by a poor young grad student who bought her very own villa in Italy and managed to get other people to pay for almost the whole thing.