I managed to do it, but I think it's unnecessarily complicated:
I used "snap points to points" (saga_cmd shapes_points 18) @Taras suggested, to snap one of my layers to the other one.
Then, since I am not aware of SAGA having a spatial join tool, I created small buffers around the points which stayed at their location with saga_cmd shapes_tools ...
Sounds like an interesting piece of work.
A simple statistical solution may be to map linear regression residuals of each house, based on distance vs property value change. (There are a million other factors here, like accessibility, linear distance isn't necessarily reflective of proximity etc)
So a simple starting activity could be:
Introduce a new ...