We, you and I, can be houses of prayer. Personally, a life lived before the Lord is a house of prayer. It is similar to the understanding of being, for example, a person of peace. Once a habit, an attitude, a right posture before God, and as a practice of the Lord within us, we begin to evidence as a person of peace or a house of prayer.
Now, we can certainly have a physical house of prayer. Mountains of prayer are found around the world. Any physical, specific, tangible, quiet place to come before the Lord in prayer is deemed a house of prayer.
But, anyone can also be a person of prayer, becoming, through a whole heart turned to the Lord months and years after years, a house of prayer. After years of abiding with the Lord there becomes an overflow of prayer flowing out from a person. The upholding of the Lord and others simply flows from the person to others round about.
This, we must become before we host a place of prayer; before we build houses of prayer let us be houses of prayer.