The security deposit -- typically one to two months' rent -- exists specifically to cover this. If a tenant causes damage beyond normal wear and tear, the cost of repairs is deducted from the deposit before any remaining balance is returned.
If a tenant needs to leave before the lease ends, the terms depend on what was agreed in the contract. Some leases include a break clause with a notice period and possible penalty, while others require the tenant to find a replacement or forfeit part of the deposit. We build these terms into every lease we manage, so landlords aren't left exposed if a tenancy ends unexpectedly.
For properties under our management, we handle the move-out inspection and deposit reconciliation directly, so landlords don't need to negotiate this themselves.