Are there many houses for sale in Marino?

Marino is a wonderful suburb bordered by Marino Rocks and Seacliff which are equally delightful. I spent a lot of my childhood in this area - it's tucked away and I doubt if houses come up for sale very often. However good luck on this one, it would be well worth the effort of trying. To cast a broader net include Marino Rocks & Seacliff. Hallett Cove and Hallett Cove Beach are probably a lot more achievable in terms of property turnover they are south of Marino and Brighton is after Seacluff

Not many. Real estate agents repeatedly leaflet my mail box asking if I want to sell, as they have a waiting list of potential buyers (they say!?).
I guess the real answer is in how Marino property prices have risen since 2021, almost doubling.