Hi @David13795 .. nice to see an active NZer...
I am assuming that your question relates to traveling not hosting.
I think the best way to get a total price is to "Request" a price from the host. Most hosts have fixed nightly/ weekly rates that are either fixed or change dynamically with seasons/ events.
With the length of stay that you are seeking, "Request" a total stay price from the Host. They then may adjust their standard rates on-line to encourage your custom. After they make the adjustment for the stay that you seek, the price to you will be reflected in the displayed price on-line.
I am not sure if you may still find monthly rates displayed... but it will give you a negotiating position to accept or not... 🙂
Our place has a limit of 10 days (no cooking facilities) so we don't encounter that question..
Best wishes.
Regards, Graham