The brickwork on the back wall of this Victorian terraced house has tilted out of horizontal.
If you look at the “coursing” of the bricks in relation to the bathroom window sill you will see it is not “level”. There are also two fine cracks running through the mortar joints. These have previously been repointed but have then reopened slightly suggesting recent movement.
There is a drain to the nearby back corner of the house. It is possible this may be defective, leaking and undermaining the stability of the structure.
As a buyer your first action should be to instruct a specialist competent drainage contractor to carry out a CCTV camera survey of the drain to establish its condition.
This will determine its condition and the course of action to then be taken. The drain could be OK, or need replacing. The foundations may need underpinning (strengthening with concrete), or it may be concluded nothing else needs to be done.
As a buyer you may have to refer the matter to your buildings insurer. There are all sorts of implications for saleability, mortgageability and insurability in situations like this. It is important to take the correct professional advice.