Wow, didn't realize that people were overlooking Insurance as a solution.
Requiring Renter's Insurance with a substantial liability coverage amount is needed.
If you agree to allowing the pet's then this is a great opening to have them sign additional
addendums and requesting a modification to the current lease for pet deposit or pet fee.
The tenants changed the original agreement by adding pets.
Hopefully you have the move in check list and/or pictures showing condition of property prior to them taking possession. You will still need to depreciate some costs of the repair unless the condition was new when they moved in.
As for the lawn I just realized my own lease does Not go into detail on Outdoor Maintenance, and
what is required of the tenant. (Mow grass, rake leaves, remove tree debris, water grass, clean gutters, or trim trees.) This will go on my addendum detailing the items listed above.
I think us landlord's overlook outdoor maintenance but this is a part of the tenants responsibility in Single Family Home of which they have access and use of these areas. When the higher then expected bill arrives to get your lawn returned to the previous states it becomes a concern.