So, it's really a subject opinion, a guess anchored in perception of economic benefits rather than any accounting allocation qualified to actual net amounts involving direct relationships with BP members.

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

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

Just invest that money to diversified allocation in a different sector, but get your accredited investors first.

Traditionally the larger and international groups have stuck to Commercial Office and Industrial, they are now becoming much more comfortable with Multifamily as an asset class that is worth allocating serious capital towards.

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).

Your property management company should have all the strategies and systems in place to keep your property occupied.If you are self-managing from out-of-state (typically a bad idea) then you want to make sure that you work with a local "leasing agent" (depending o  the size of the property) and you have a solid budget allocated for marketing and ideally get to the point where you have a waiting list.

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

The problem when you just borrow money not allocated to a specific property is; how do you decide when to pay it off?

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.