As Mel rightly says, there is no mandate in the US to install a 406/121.5 ELT. But after years of indecision, Canada has mandated it, although for recreational aircraft, the final implementation looks to be 2025. So think about where you might want to fly.
Since the satellites no longer listen for 121.5 ELTs for SAR purposes, and haven't for about 10 years, I don't know why anyone would install one if they are buying new. Only other aircraft and airlines listen to 121.5 and they have no way of determining the location, only that they have received a signal.