This is something I heard once from a caller on a financial radio program. What does it mean and what is the logic behind this statement?
Putting debt out long means to borrow a sum of money paid back over a longer period of time than you could reasonably pay it back.
It should be important to note that this advice only applies for fixed rate loans (meaning your rate can't change for the life of the loan without you explicitly changing it).
The logic is that if you can borrow money when interest rates are really low, there is a good chance you can find an investment that has a return higher than the interest rate on the loan. It also means that when/if interest rates go up in the future, a simple savings account may even have a greater return than your loans interest. The advice suggests to borrow over a long period so you are paying less interest per payment, and gives you time to find a proper investment without having to pay too much interest during that time.
Putting debt out long is getting a longer term while interest rates are low. For example, taking out a 30 year mortgage instead of a 15 because we are at low rates for mortgages and you are unlikely to get this good of a rate in 10 years.