It is critical to ensure the landlord/agent keeps a regular eye on the property, and especially get the tenant(s) to inform them of any problems. This will hopefully stop any minor problems becoming major.
It is also important to remember that access to the property is only with the tenants consent, it is critical not to abuse this consent. Whilst the law states that access can be gained after giving a 24 hour written notice of access, if the tenant refuses access the landlord cannot enter the property.
The best way of gaining access is to have a clause in the AST stating that regular inspections will be carried out. Then the landlord/agent can contact the tenant stating that the next inspection will be at time on date, and that the tenant can be present if required, but doesn’t have to be. Unless the tenant responds to state that access is refused it will be OK to enter.
Recommended intervals for inspections are within the first week, to ensure all is OK, and that the tenant has understood all the instruction upon check-in. After that it is probably best to arrange quarterly visits in the first year; perhaps 6 monthly thereafter.
The critical thing is to retain good communications with the tenant(s).