Miapuff, good evening.
OK It is difficult for us over here to understand repair practices in the US also we have no understanding of ground conditions and original build specifications
There is [an obvious] large degree of movement in the porch, However, the movement does not at first appear to be downward [Subsidence] rather, especially in Pic 2 it appears that the bricks have been displaced outward to the left hand side of the Image posted, by what could be 25.mm [one Inch] Minimum, this is noticeable if you copy and paste the posted image into a format that allows zooming in Etc.
Going back to Subsidence at first glance [Pic 2] the base blocks appear to be sensibly level along their top surfaces where the blocks meet the brickwork.
In your Image Pic 3 there is a definite almost vertical crack in the base block, which is mirrored internally Pic 4 such distortion is more representative of Subsidence [a crack that starts at ground level]
Now where to go?
As johnD above price considerations? Etc.
How long has the property been offered for Sale? sometimes a steer on something amiss where other prospective purchasers have looked, investigated and walked away?
If your heart is set on the property / location then you will probably be looking at serious $$$ to effect a repair?? to the porch, such things as a Soils investigation to determine the bearing pressure of the ground below the porch, Structural Engineers input [and cost] as well as a Builder to remove and re-build the porch.
On another front how would a prospective lender react to this situation? over here it is unlikely that a mortgage lender would be up for the challenge?
If it were me, i would walk away?
Ken