However, in my research of the neighborhood the property is in, I found Trulia's "What locals say about (neighborhood)" in which features such as "Kids play outside" and "People would walk alone at night" get a percentage ranking I assume from crowdsourced voting. 

Should I do a percentage split instead of a set price, maybe a 60/40%?

Or charge each a percentage of the water bill per month as I do on my units.

This is normally expressed as a percentage and that percentage is of the ARV.

With a straight equity split, investors are given a defined percentage of the property’s cash flow and equity on sale, often defined as “60-40” or “70-30.”

With a straight equity split, investors are given a defined percentage of the property’s cash flow and equity on sale, often defined as “60-40” or “70-30.”

Purchase price: $85,000 Cash invested: $17,000 Solid Brick Duplex in a highly sought after neighborhood with a large percentage of rented property.

Black race population percentage significantly below state average.

They want you to pay a small fee depending on how much you borrow, it's a percentage. 2 people I know has been banded from 3 groups I'm apart of because of fraud practices.

How much, either percentage or amount, should be good to give her?