I agree with josh, the deal seems thin and the only money you're going to get in your situation is hard money, so be prepared to spend 9-12% and 2-4 points. Even then they won't want to finance you for too long, expect 6 months - 1 year.
If you insist on doing the deal, then the best case scenario is if you made the seller financing you are getting from the seller assumable and include a subordination clause (which needs to be negotiated now) then turn around and sell the property as-is to someone else with good credit and let them get a bank loan for a 70% 1st. Most likely if you are trying to sell the property for more than market value, you will need to create a value for your new buyer, that can be done by you creating a third mortgage that you own, so the new buyer has little to nothing down. It's a complex transaction, but it is doable. Lastly, I would start advertising the property now on craigslist et al, to see if you get anyone interested in that scenario.
Curiosity question, I know that a lot of times hawaii properties don't include the land. $150k for a 2year old house seems like an amazing price, whats the catch? Is the land leased?
