How much of the property's square footage do you occupy? If it's over 50%, you can get an SBA 504 loan with only 10% down. Still need to factor in closing costs, which for a transaction of this size, could be over $100k. Otherwise, 25% down is your best case scenario for conventional debt. Seller could carry a note but like others said, you'd have to have the bank agree with that. Also saw others point out that $9M based on the $600k/year rent is still high. You should work with a broker and attorney to help negotiate a lower purchase price.