Maricopa county requires any area of a lot that is driven on or used as parking to have a minimum of 1/4 plus rock spread on the surface to minimize dust.  

I'm concerned this could be a big liability for my next tenant so I'm planning on raking the entire surface out and running a magnetic roller over the top to grab anything I miss.

To get people out and raise rents, owners and investors in Metropolis are having to pay "severance packages" for tenant of 5 - $10,000 / $20,000 / $25,000 sometimes more depending on surface and other factors.Your solution is to build model to sell these unit to the tenants (on a massive scale).The model you come up with to tackle these 550 low yielding units you portfolio is the following: Instead of using bribes to kick people out you decide to "subsidizing tenants'" into 1st time ownership. i.e. you want to help them to buy there own flat (at least the tenants who are decent earners).Instead of using money to get tenants out, the model would be to help them get financing by sponsoring a portion of the deposit on the Mortgage.

The soap reduces surface tension, so the sink and drown.

Sure 9% cap rate looks good on the surface.  

If not, you're gonna be stuck researching everything on the surface, lost in macro economic reports and blog articles listing "the 10 best neighborhoods in X".

However, on the surface with only a $30K spread from acquisition and ARV, that's not much to work with if anything goes wrong with REHAB or buyer demand drops.

I expect the tenants to remove their belongings, wipe down surfaces, and vacuum. 

Refinished hardwood floors myself & painted every surface.

Appearance It usually only grows on flat surfaces, and has a powdery or “downy” appearance.