We plan to rent out the basement on a medium-term basis - we are going to install a full kitchen down there, put a lockable door between upstairs and downstairs, fence off a private section of the yard, and there is already laundry down there, so it will essentially be an up-down duplex with a separate walkout basement entrance.

@Donnie Maguire Just to be clear you have two separate and distinct issues. 1) getting your sister in law off the title (deed) 2) getting your sister in law off the mortgage. 

I have a tiny condo that only has bedroom closets.

Others do not ask.I have two properties in the same area and one when I PCS’d.

Here are some differences between the two to consider: HELOC: It's a flexible, revolving line of credit, allowing you to borrow as needed and pay interest only on the amount you use. 

She is 1/3 owner of a two family with her grandmother and father.

My two question are:Have other agents had similar type offers on any listings? 

Doesn’t matter if door is self locking, he props it open with umbrella or door mat.

ClairI have two duplexes in my portfolio and live in one.

I now own two SFHs and three MFHs (all out of state) and am continuing to grow my portfolio.