WiFi in a Condo

My neighbor posed a question to me. He inquired since I have a DSL connection would I be willing to have him access it via a wireless connection. I said sure. However, there’s the issue of going through the block walls, not to mention our metal studs; which are an issue. The scenario being he is located diagonal of me, but not above my next-door neighbor. His unit is above my next-door neighbor’s next-door neighbor. Is this possible? It sounds intriguing.