There's really one answer to this, but it has about 1,000 sub-parts: a landlord can demand possession for any material breach of your lease agreement. What these breaches consist of is governed by the lease itself.
Failure to pay rent is naturally the most common such breach. Others could include violation of the neighborhood association covenants, violation of some relevant law, violation of some specific restriction (such as a covenant not to keep pets in the home or a promise not to sub-let the house), etc.
No attorney-client relationship or privilege is formed by this communication.
The reasons that a landlord may evict a tenant depends on the contents of the lease agreement between the landlord and tenant. The most common reasons for evictions are failure to pay rent, or being a nuisance; however, some lease allow for eviction merely because the landlord wants the property back (on a whim) but the tenant has refused to return possession.
The reason behind an eviction is only relevant if the tenant intends to argue that the reason given is not valid. What matters most is that the landlord follows proper procedure in seeking that eviction.
I hope this answers your question.
~ Kem Eyo
The above answer is a general explanation of legal rights and procedures. It does not constitute legal advice. Nor does it establish an attorney-client relationship between the individual posting the question and the attorney providing the answer.