I think my PM co does credit checks, references, criminal background, and work history.I googled "how to screen potential renters" and found on line services and interesting information.

When you run a credit check and criminal background check, what is acceptable?

Also would like to know if they have criminal history. 

@Nick Wight I would make sure to get 3 bids, check out their current/past projects in person, and do all the other due diligence necessary before hiring anyone (criminal/civil record, insurance, etc.).

Make sure their criminal history checks out.Another key factor is employment history.

Does the sponsor have a criminal record or civil judgment on mishandling investor-money?

It won't go well unless you are this type of LL and accustomed to dealing with druggies and criminals.

I'm wondering what services you all use to screen tenants in Seattle, in order to conform with the "second chance" law preventing criminal background checks (or even asking questions about criminal history). 

Some are drawn to the criminal lifestyle, some got on the wrong track for a only a short while, and some made one mistake that cost them dearly.

Criminal element handling depends on the situation.