The description indicates that they would like a long-term lease - this as opposed to the short-term, seasonal approach. Different homeowners have different ideas and desires for the rental properties.
If an owner says long-term, that customarily means at least one year, and generally they would want longer if they can get it. If you are willing to go more, the two years, say, it is possible to negotiate better terms on the monthly rate.
It is a very good idea to work with an experienced agent for this process, to assist you in getting the best value for your rental dollar.