Getting beyond the quesiton of 'what area is safe' is not only relative to crime statistics in the area, but other 'perceived safety' of a neighborhood. I have a vietnamese investor client who prefers to rent her units in the vietnamese communities as she feels it is 'safer'. I have someone who's family lives in an area that many others might consider 'less desirable' but she knows well and wants her kids to remain in the same school and close to what is familar with them.
As realtors, we cannot designate areas as 'safer' than others, for both legal reasons and for logical reasons as even the million dollar home areas experience some risk for safety. We can, however, be the 'source of the source' and provide you resources where you can learn information such as crime reporting, tenant laws in terms of nondiscrimination, and proper obligations of landlord/tenant relations. school testing scores, and various other information where you can become informed in selecting investment properties that meet your interests. It's best to be sensitive to legal issues involved in buying investment property, and the ultimate selection of tenants for those properties.
If you are specific as to your question on what information you would like to review, I'm sure we can give you even more resources to help.