The short answer is that even if it is all legal, creating a partnership that gives you more gain than everyone else means it's not an equal partnership.

If you can take the cash and reinvest into equally profitable and "easy" property, then that's when it is worth considering. 

If they are VERY professional, they will have their processes in writing as verification that it is enforced equally and fairly by their entire staff.6.

No it actually is better to have a property in a state that closely matches your state of residence's income tax if all else is equal. 

I’m asking if we were to decide on this first property that we don’t want to set up an LLC, is there any sort of additional partnership agreements to be made beyond the joint loan between us being of equal contribution?

Per the owners P&L, these two expenses together equal $1800/month. 

I never fell into the belief that I could start with $0 of my own money, it was more disbelief that it is never talked about.

But that she is unsure how to equalize it or show a personal loss between the $250k contract cost and $375k value of the equitable rights as they are not in the same entity, and as I don’t own the property, she doesn’t know how to put a value on the contract for tax purposes.

I have received net cash equal to the down payment and all the equity would be additional profit.

If there are two tenants renting from me that aren't married, I try to make sure at least one of them meets that standard on their own for situations such  as this.3) My lease states that all tenants are equally responsible for the entire rent, not that each tenant is responsible for half etc.