I sent a letter terminating our agreement. 

Have your attorney do two things simultaneously: (1) draft a letter to the tenant called "notice of termination and demand to vacate" and (2) file an unlawful detainer suit seeking possession and, if possible, damages. 

After 3 years of renting to her and finding out she was completely FILTHY, I had to choose peace of mind over money so I terminated her lease.       

IF you go through with the deal (I would not); then when their leases get close to the end, terminate every single one of them.

Rental Housing Association (RHA) also regularly provides classes and resources for managing all this.Make sure whatever lease / rental agreement is written clearly indicates that it will terminate a month or two before your neighbor wants to come back.    

We now have a lock box with a key inside attached to the gas meter, just in case the batteries fail.

Make sure it explicitly explains the process for termination if you are unhappy with their services, but especially if they violate the terms of your agreement.3.

He has 3 years to go on his 15 yr term. In

Make sure it explicitly explains the process for termination if you are unhappy with their services, but especially if they violate the terms of your agreement.3.

Should I send her a lease termination or 30 day notice ?