Yes, it's quite possible. But are you confident that you can get a 75% loan from your bank in this economy? Many banks are offering very low LTV's on commercial properties. Some as low as only 65% or 70%.
So that's your first step. See what terms you qualify for from a bank on the first loan. The bank typically won't care if the owner takes a second loan on the property. As long as the bank is in first position, they are protected. Then see if the owner is willing to make a second loan for you.
Be advised that if the owner agrees to take a second position loan on the property he will expect a significantly higher interest rate on his loan because of the added risk involved with his subordinate collateral position.
So, your first position bank loan might be at 6%, but your seller carried second loan may be at 9%.
Compare that with the interest rate the seller is offering in order to carry the entire purchase price, you just might be better off with one loan (from the seller) at 6.5%.
Sep 13, 2011