Fire Station No. 5, one of the city’s oldest, is expected to close its doors within the next three years. That closing, the mayor’s office said this week, will result from a high-profile swap of Riverside Avenue property between the City and Fidelity National Financial. As part of that proposal, Fidelity has two options. After the City determines the location for a new area fire house, Fidelity will take title of the building. At that time it can either choose to rehab the more than 50-year-old structure with money out of its own pocket or it must alert the City that it has no plans for the building. If Fidelity chooses the latter, it must pay what it would cost to demolish the station to help pay for its relocation to an as-yet-undetermined site elsewhere. The City said that at this time there is very little chance, if any at all, that the fire house will be torn down.