The property does need rehab work to the floors, kitchen and bathrooms, some window panes, some roof shingles need replacing, and entire inside paint job.I just met the contractor this Monday July18th, and am awaiting his estimate.

Aside from that the windows are all double pane and up to code..  

The panel is not know and tube.

No missing flooring, no leaking roofs, no broken window panes.  

Take a Sharpie and use it to  look like a window pane or two is cracked)

I paid $3600 for 7 dual pane double hung from Window World.

They may have a suggestion.When it comes to family, there is no business or buck ($$) worth straining that relationship, so I would make sure you have her blessing before moving forward.

We did quick inexpensive fixes and rented to a low income person who applied for weatherization and the program put in new double pane windows, a new cooling system and insulated the attic. 

I found I could get new glass panes 1/4 of what they want here by shopping in north Texas.

If some of the panes are broken then just get them reglazed and don’t replace the entire window.Also sounds like in your situation you should be cutting the grass as well.