What Criteria should Tenant's meet in a C Class Area ?

[Carl Gryska]

I own 5 SFH in a C class area of Phoenix AZ. My first tenant in my first home is still with me going on 3 years but one of my other homes is going to have its 5th tenant in a little over 2 years. The difference of income on these two properties is of course significant. What is a realistic criteria for C class property? FICO score, back round check results, proof of income etc? My manager has also been renting my houses for $850-$895 and we are getting $600 for security deposit. Shouldn't security deposit be the same as one month rent ? Should I use someone that screens tenants for landlords? My vacancy's are always rented quickly but I am willing to pay more and wait longer to find a good tenant that will stay for a while and pay rent on time. Anyone with experience, please help!