The height of the tree is not decisive for your tree house – much more important is the diameter of the trunk, which should be at least 30 cm (better 40 cm), depending on the size of your treehouse!
Also make sure that the proportions of the treehouse and crown volume are right, the tree house should not visually “smother” your little tree.
With small-growing trees with a low crown, such as fruit trees, it is often better to build the house on stilts.