For building gaps, I would try to make a deal with the neighbors. Same with water.
We did the same.
Tapped electricity from the neighbor (cleared beforehand), bought the material on eBay Classifieds (cables with sufficient cross-section and matching construction site power box with a calibrated meter)
Total expenses of about €400, which we should more or less get back when selling.
Real loss should maybe be max €100.
Although the boxes and cables sell like hotcakes.
In the end, the neighbor is settled with and maybe he even gets a hundred as a thank you.