What to do when an investors shortens the amount pledged?

[Michael D'Elia]

My business partner and I are under contract for cash deal on a Duplex that is attached to separately zoned land. Its an amazing deal and everything is set to make a very nice profit developing. Unfortunately, our investor (who happens to be related to my business partner) decided he no longer wants to put the $600K he initially pledged and instead wants put only $300K down. Yes, rookie mistake not having a lawyer draft up a contract between him and myself but we thought its ok because its family. That mistake aside, what would you do if you needed to come up quick with roughly $300K with no time for an appraisal and closing only a couple weeks away? What are some creative ways that I can source this kind of capital? Looking for suggestions.