This is a paid asset, but now you can download Pro Building Pack v5 for FREE, but please remember this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
Pro Building Pack v5 v1.0
Pro Building Pack-v5;
This package contains 11 building meshes with 2048×2048 texture resolution.
v5-building_01: polys:983, tris:1962, verts:996
v5-building_02: polys:275, tris:548, verts:550
v5-building_03: polys:420, tris:856, verts:440
v5-building_04: polys:147, tris:294, verts:164
v5-building_05: polys:735, tris:1454, verts:904
v5-building_06: polys:192, tris:432, verts:336
v5-building_07: polys:133, tris:274, verts:160
v5-building_08: polys:160, tris:320, verts:185
v5-building_09: polys:234, tris:492, verts:284
v5-building_10: polys:396, tris:792, verts:466
v5-building_11: polys:279, tris:592, verts:448