Waterfall Structure Help

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Hi everyone, was hoping someone could help me! 

Im trying to set up a model that calculates Project Profit Margin (unlevered), Project Return on Cost (unlevered) and IRR for the problem below:

It's a condo development that has costs for 32 months then one lump sum of revenue once construction is completed.

Financing:

Loan of $18.5m,
Purchaser deposits of $2.5m
Equity - investor - $3m
Equity Developer - $1m

Costs:

Land - $7m
Soft costs - $6m (incurred equally every month)
Hard costs - $12m (incurred equally every month during construction)

Revenue:
$31m one month after construction

Waterfall Structure:

•Investor will contribute 75% of the equity and developer will contribute the remaining 25%

•Equity will be returned as follows: (1) both partners will receive a return of their equity pari passu, (2) 50/50 until Investor receives an IRR return of 20%, (3) 40/60 in favour of developer thereafter

The loan bears interest at 4.25% per annum

I'm having a hard time with this one :(