With out knowing all the details... Sounds to me like you need a new property manager. There are many reputable firms out there. $9000 would cover a huge amount of repairs. What did these tenants do?
One way to deter bad tenants is to do first, last, security, and credit check. I find as soon as you tell people you do a credit check the bad ones tend to run.
If I can be of further assistance feel free to call or email me.