All numbers are per 100,000 residents, anually:
Murders: 46
Rapes: 40
Robberies: 763
Assaults: 1440
Burglaries: 2060
Thefts: 2430
Auto Thefts: 2280
Arson: 88
Aggregating "stealing" crimes, gets you 8,970 or about 9% chance per year. Adjust this for being "those rich dudes from out of town with all that electronic stuff" coupled with the $100 houses not being in the better parts of Detroit and I recommend good offsite backups and a personal philosophy that does not form attachments to material possessions.
I stayed away from that, but at .1%/year, within ten years you will attend the funeral of murder victim. Murder will be "real" for you, not just newspaper fodder.
That same case can be made against any city though Detroit's numbers are worse than most. However you would never have urban renewal at all if people let that stop them.
I have friends doing urban homesteading. Your first purchase should be an alarm service followed by web cameras watching the property. The goal is to intelligently cut your potential risk, they haven't had any problems - so far.
But what is the throughput of people in detroit? Detroit has fairly few residents compared to the number of people who go into detroit to a casino/dining/sports game. The chance of one of these robberies happening to a resident is much less than 9% I would argue.
Also, you're forgetting about the "Broken window effect" which says that crime flees an area when the surroundings simply look better.
