In essence it's a downward spiral.

If China goes into recession also bringing down the U.S. economy into a recessionary spiral, immigration and foreign investment from China (demand) will also slow down. 

The ferry is in a downward spiral of fare increases and decreasing ridership. 

My pantry is pretty small though, so there is that:Spices, cooking oils in cabinet by stovepots/panssmall appliances that I use often like blender, spiralizer, etcpyrex/tupperware storage containersziplocs, parchment paper, foilhand towelspull out drawer for trash/recycle << I think this is importantmicrowave/convection on bottom if hiddendishes, obviouslyglasseswine glasses << yes, I just put those in their own category.

There was a spiral staircase where the treads were just inches wide, so you went up the stairs on your toes and came down sideways, clinging to the wall.I loved that house, but never heard anything from the resident ghost.

So at one point they will have to stop and that leads to increasing interest rates and down we go the spiral of doom.

My wife and I are wondering if it makes sense to add a spiral staircase to one unit so they have a fully private unit top and bottom and no shared area.

If you do not, this tenancy will continue to spiral downhill until they owe you months of back rent and disappear into the night.Think back on your first interactions and screening process with these tenants. 

Consequently costs spiraled, the schedule got blown out, and tensions ran high. 

@John Thedford  I think what has caused this so called business of wholesaling in many markets to spiral out of control..