Sectional layouts
A friend of mine was hosting an operating session, and as we were about to get started he apologized to the group. "Sorry, but this layout is only temporary," he said. Someone else pointed out that all model railroads are temporary, it's just that some are around longer than others. If you know you'll have to relocate in the future, or even if you just want to be prepared for that possibility, you can build your layout in sections that you can dismantle, move, and reassemble.