How much should an investor make?

[Rebecca B.]

Here's the scenario:

Rebecca and Rachel buy a property for cash each putting 50% into it. Rebecca intends to buy out Rachel within 6 months of the sale.

The property costs $55k. Repairs $10k. They put in $32.5k each. Property rents out at $900/month. ARV $80k.

Rebecca gets financing at the LTV 70% and holds onto the property as a rental.

What return should Rachel get on her investment? They're sisters so Rebecca wants to be generous. 

Also, would I be correct in thinking that until she buys Rachel out that they should be splitting the profit from renting it?