How do i make this deal work

[Brett Arends]

I need your help! Hello bigger pockets members. My father and I recently started investing in real estate. We own 4 SFHs and now have a 4 plex and a 12 plex with another 8 unit building under contract. We recently agreed to a price on a 31 unit building but the seller backed out of the deal right before the purchase agreement was signed. The property is 31 units (14 - 1 bedroom 17 - 2 bedroom) and the seller and I agreed to a purchase price of $950k. The seller was going to carry a 2nd on the property for 20% of the purchase price with a 30 year amortization and 3 year bubble and I would put 5% down as well. I already have approval from the bank as well. After agreeing to the price the seller spoke to his son and they then decided they wanted me to put 15% down if he was going to carry a 2nd for us. The issue is we don't have the liquidity to put 15% down at this time. Does anyone with more experience than I have have any ideas on how to make this deal work? Any feedback or ideas would really help me out. Thanks!