I had to do that about 10 years ago. My evaporator drain clogged and my old AC didn't have a float switch. My evaporator is upstairs; it was a day before i found out about the leak - had to change out the sheetrock behind the evaporator, in the ceiling of one of the bedrooms, and the ceiling of the garage (live in townhouse).
When I redid everything, the first thing I did was to wire in a float switch. And after that, I've put leak sensors wherever I there's likely to be a leak. A few weeks ago, I had a leak in reverse-osmosis water purifier under my kitchen sink - the combination of a leak sensor and automated water valve cut off the water before any real damage (my kitchen is upstairs too).