In a similar fashion, if you can imagine how much landscaping and underground infrastructure is in a golf course as compared to the clubhouse, that will give an indication of why an extremely high percentage of the property's value is allocated to the land improvements.

Included 20% capex allocation in my calcs (which might be low. 

Really depends on your budget, motivation, and time you can allocate to it. 

Most are not as good at determining the accounting and tax allocations issues. 

However, how different syndicators allocate depreciation varies widely.  

Via the IRS:Cost segregation studies are most commonly prepared for the allocation or reallocation of building costs to tangible personal property.

My household income allows me to save $20k post tax dollars a year and ~40k pretax dollars per year for allocation to real estate rather than stocks/bonds & speculative instruments. 

Since 1/6 of the property is her residence then you could probably allocate $250,000 of the sale to her primary residence.  

As a partnership, the income and expenses will be allocated to each partner in accordance with their share (or as given in the partnership agreement).

I would within the timeline of your states guidelines send a letter accounting for how the deposit was allocated.