The thing that you didn't mention was the size of the tire that the potential buyer uses. If the assumption is that they are using 25c, it would work, but tubes are so cheap that I wouldn't do it. If you blow up a tube outside of the tire, you'll notice that the area that does not expand proportionately to the rest of the tube is around the valve. While the rest of the tube will expand to fill the space, there will be more stress around the valve area because it's necessarily less flexible around the connection - a weak/stress point as well. Tubes are so cheap, I don't even know why anyone would bother with this vs. potential failure of the tube on the road.