Original image
step 1 of 6
Retouch out all the horse's friends
step 2 of 6
Desaturate image
step 3 of 6
In separate layer add Mansion image
step 4 of 6
Position mansion/house image
step 5 of 6
Add layer mask and start removing part of image you don't need.
step 6 of 6
Desaturate building and start blending. I saved a duplicate copy and flattened it then I used clone tool and patch tool to blend my image. Added some contrast and a bit of red and yellow.
Final result
