I've made it a point to look for people with thousands of posts to see how low their member rank is. I think you'll take the cake sir, 19 is hella low.
I have not read through the whole thread, but I have a friend who buys and rents houses. His rule of thumb is yearly rent should be 1/10 the price of the house. So basically it takes a little over 10 years to pay off the house, then everything after that is profit. So if she is not paying 1/20th of the price of the condo, then its not a fair deal.
Personally, I'd never buy a property with plans to rent part of that property to another person. How long do you really plan to be in a 2/2 condo? If you can't afford to buy your own place, rent something you can afford, with either a roommate or by yourself.