You can sell your building for $200,000.
Alternatively, you can lease out your building. The lessee will pay you $2,000 per month. You will have to budget $700 per month for upkeep, attention, and so on. At the end of the 20-year lease, you expect the building to be worthless, but the land to have a residual value of $150,000.
Your cost of capital is 0.5% per month. Should you sell or lease your building?