Last night there was a violent storm and my basement window caved in, and violent rain crashed the windows and did considerable damage to the basement. question #1: what is my tenant's insurance responsibilities for this property?

Bottom line, which I think we're all in violent agreement about :) ... materials procurement is a complicated game of strategy and the "right" answer varies from job to job, material to material, business to business, and town to town.

If those men with guns were to go away, would other men with guns show up and commit violent crimes?

Think of the most violent areas of Detroit.

Prefer someone with violent criminal history & as many noise complaints as possible. 

I can deal with tenants who are violent.

I mean, I guess if it had been a different set of circumstances, like a violent crime had occurred that's one thing.

By the way if you hear I died suddenly and violently and the police have no idea who did it, tell them to check my wife's alibi.

Red flags for us on a background check include: evictions, violent crimes, felonies, credit issues that involve the non-paying of everyday bills (utilities, cell phone, etc.) and very undisciplined use of credit.

The guy has a potentially violent, or at least threatening,  history.