If the lumber used for framing (especially the beams across) are not up to support the additional weight of a bathroom with a full tub of water...
if so, you need structural engineer inspection and apply permit.
otherwise:
2-3k for wall, paint
1k for floor
2k for bathroom+plumbing
1k for door, window, steps...
if so, you need structural engineer inspection and apply permit.
otherwise:
2-3k for wall, paint
1k for floor
2k for bathroom+plumbing
1k for door, window, steps...