We have only one base currency in the system which is EUR. User browsing the properties can change the currency at bottom of the page by selecting the preferred currency. In that case we will display the prices in that selected currency with live exchange rates from xe.com. However this is for the display only and doesn't change the currency in the system.
When user goes to pay, they can pay with any currency PayPal accepts, but it will be converted to EUR with PayPal exchange rate at the time of the payment.
Furthermore: the payment to host will be sent in EUR, but receiving bank account or the PayPal account can be in any currency.
We are aware that this may impact some loss or gain in transactions as there can be long time between payment from Guest to Payout to the host. However, with this scale we are operating, we have not found any financially feasible multicurrency solution to change this.