Will it be correct if I would say "This house is selling" meaning that someone is selling the house? Or I should only say "The house is being sold" to be understood right?
The house is being sold.
means the owners have put a single house up for sale.
The house is selling.
can be said to meaning there is keen interest by several buyers in the house.
It can also be used in the plural to mean houses in general
(The) houses are selling.