Best way to optimize taxes for new construction of investment property (for flip)

[Muhammad Kashif]

I am considering working with a property developer in NJ to buy land, build a duplex/triplex and sell it (6-9 month time horizon).  Is there any creative way to avoid/reduce capital gains tax on the sale ? From what I understand, a 1031 exchange doesnt apply in this case, and so I will have to pay short term capital gains on the appreciation ?(after I deduct all the labor/material costs). 

Is using a self-direct IRA to fund this venture a way to defer taxes until retirement ?

Will the capital gains in this scenario be considered passive income from an IRS perspective ? (I am a silent investor, the developer is doing all the heavy lifting, and we split profits at the end)