Trying to build a nice deal for investors – Strata approved block of units Sydney needs finance

I’m interested in getting some feedback on a deal I’m proposing. Thought you guys might be able to help.

Here is the background;
Two years ago I bought a block of flats in Sydney’s Inner West. It’s well located in a side street but next to shops (incl McDonalds, Subway, Dominos and other restaurants) and transport. There are six two-bedroom units in the block (all on one torrens title) and it’s in pretty good condition.

The plan is to strata subdivide, renovate the units (two of the units will become three bedrooms units by integrating shared laundries) and flick them off singly for a premium. I have a DA approved for exactly that and earlier in this year I renovated three of the units to a pretty high standard (might have gone too far).

Rents are currently $290 unrenovated and $370 reno-ed.
It was a good buy, and is now cashflow positive. That’s fortunate because I started a postgraduate course at uni this year and as a result haven’t been working. Consequently I’ve run out of cash to finish the project.

So here’s what I’m thinking;
I need about $280K (roughly the current value of one apartment) to finish the block and have the units ready for sale. (This involves reno-ing the other three interiors, extending balconies, fire provisions and carports).  This work could be done in four to six months. At that point I believe that each unit will sell for $350 – $380K .   

Wondering what you think about pre-selling one of the units so effectively the investor will benefit from the previous development work I’ve done and the capital gain on resale?

There are a couple of ways I’m thinking this could be done*,
1)    set-up partnership split in proportion to current values vs investment,
2)    use an option fee arrangement  on the purchase of one unit – obviously this would need to be a substantial portion of the total value to get the project to the sub-divided stage where contracts can be exchanged.

Are there any other more elegant ways to achieve security for the investor while reducing (or deferring) the costs?
At gross returns of maybe 25% over four to six months, I think it could be pretty attractive to the investor.

*Property is held by me personally so I’m looking for a way to keep the transfer fees to a minimum for both me and the investor.
Look forward to hearing what you think.

Thanks.