@Jason MeadowsFor the garage they did have to go through some Engineering to get stamped plans saying it was OK to have people up there, and from that came construction to sister floor joists, do spray foam insulation, Sheetrock, paint, flooring, etc.

I have shared ownership with my sister (whom is a minor).

My sister teaches in the Whitewater School District and may know someone if you want to PM me.

When i purchased my first home I noticed that my mortgage was cheaper than what my sister was paying in rent for an apartment in my area.

First, I broker apts and have done ONE student housing deal in 20 years, so not an expert by any stretch.In PDX, a lot of the weak-sisters like the for-profit liberal arts colleges are having a real tough time.  

My sister and I each have 50% ownership in 20 acres in Poolville, TX. 

My sister house is about to be paid off by the end of this year.

His sister has his Power Of Attorney, and said she called a title company and was told I’m making this issue up, so she doesn’t believe me.

I have a friend who's sister-in-law inherited 27 sfh rentals.

Your engineer can likely provide some recommendations on how to decrease (not eliminate) the deflection of the joist(s), by jacking up the original joist(s) as mentioned above and sistering another joist onto 1 or both sides of the existing.