[westbywest]

Legal expenses, if the eviction sees court challenge. Especially if any claims of discrimination are sustained against the landlord. Also, labor cost of emptying the unit, repair/cleaning to make the unit ready for a new tenant, etc. Folks being evicted usually aren't in a cheery mode about it, so stuff might get broken.

[JamesBarney]

I don't think those are externalities because the two parties to the contract are the ones bearing the majority of the costs.