Houses behind trees is not an idiomatic expression in English, and as song lyrics (like poetry) are left to the listener's interpretation, there isn't necessarily a single correct way to interpret this lyric.
There is, of course, the literal interpretation of a house behind trees, perhaps behind a hedgerow for privacy, or perhaps behind a tree garden, or even on a street which is lined with trees. These would be the mark of someone with an abundance of land, and perhaps the money or pedigree to accompany it. This interpretation is congruent with the preceding lyric mentioning the vanishing point appearing, suggesting a plot of land so large that the house would be far in the distance, perhaps even unseen, from the gate.
But the phrase also recalls others that reference bourgeois living: along quiet tree-lined streets behind white picket fences across well-kept lawns, in what The Economist will invariably call a leafy suburb. These clichés do not necessarily evoke a life of wealth, but of order, gentility, and security when used positively— or conformity, vapidity, and phoniness when used negatively.