Landlords have an obligation to keep a property wind and watertight and tenantable and heritable. Vermin, roof leaks and damp are not acceptable and you should inform your landlord and ask him to deal with it. If vermin make an appearance after you move in, your landlord can hold you to account for it and may claim that you have left food around and have not kept the property clean.
If your landlord requires access to the property, they must give you 24 hours written notice-whether it is to do repairs or to show prospective tenants around the property. They absolutely cannot let themselves in without notice unless there is an emergency such as burst pipes or a gas leak. On the other hand, as a tenant you are expected to provide reasonable access when requested.
If a landlord wishes to evict you, they must first obtain an eviction order from the court. After this, it is the court who decides whether there are grounds for eviction. If you landlord evicts by any other means, it is illegal.
When you move into the property, ensure that you have a copy of the written agreement or lease. If your landlord does not provide you with a written lease then your lease is an unwritten one and you still have rights and obligations with regards to the property along with anything you have agreed verbally you’re your landlord.