Insufficient, unstable, somewhat non-garnisheable income. 

Unstable ones or tenants I suspect might leave in December, if they don't want to sign a lease that gets us to good weather we add the premium; this way, if they leave after Thanksgiving we've covered the extra vacancy a little bit, as December-February are hard months to fill. 

Someone from away is more unstable as they will be new to the area and will be incurring additional costs, it may be a new job or if self employed the business may be negatively impacted by a relocation.

@Kevin Allen - These are for Chicago, but likely very similar for other local housing authorities...MOST COMMON FAIL ITEMSInoperable light fixtures and improperly wired electrical outlets (reverse polarity, open ground, hot neutral reverse, etc.)Deteriorated and unstable paint on surfaces (peeling, cracking, chipping, etc.) in units built prior to 1978 where children under the age of six reside or will resideMissing, inoperable or incorrectly mounted smoke and carbon monoxide detectorsBroken or inoperable windows (cracked glass panes, broken locks, drafty frames, etc.)Exposed electrical wires/connections (light fixtures missing globes, electrical junction boxes missing cover plates or knockout plugs, breaker boxes with open sockets, etc.)Broken/faulty door locks and drafty doorsCutting hazards, including protruding sharp nails pipes/metals objects with jagged edges,deteriorated sheet metal, cracked glass blocks on windows,etc.

You honestly dont understand that some places are nearly unrentable, extremely unstable, excessively crime ridden with wide pools of potentially horrible renters?

Credit cards are more unstable than helocs

They're not unstable but they move a bit more than I like. 

Otherwise, you are dealing with the most transient and financially unstable renters out there.

The one time I was thankful to have mine was during an eviction of an unstable person.

For example, our smart lock solution worked great at 30 listings, but by the time we hit 50 units it was glitchy and unstable.