@Theresa Harris
So I think I'm still not explaining this correctly.
My brother does not live here. Just me and my roommate. So we're not short anything on the mortgage. I pay 900, roommate pays 600, brother pays 300. My bills have doubled because I used to rent all inclusive for 450. We looked at building a 2nd onto the house but the cost of the permits put it over the cost of her building something separate. She's going to spend about 120k to build the house and she's paying the difference of property taxes so that's covered. We're not going to ask her to pay any part of the mortgage.
We would not be able to rent this house out for 2k a month. Is that where you're getting that figure?
The deal with the 2nd house is that she's paying for it so she won't have a mortgage payment herself. This is for her to live almost free and clear. She'll have her monthly bills and years taxes for the house. She's getting older and getting something from her for profit is not what the 2nd house is about.
Are your calculations different based on the info about the mortgage being covered each month?