If you go this route, be forewarned: not all SSD enclosures work. Do a bit of research on Raspberry forums before making any purchases. Also, Pi 2/3/B+ sadly do

If you go this route, be forewarned: not all SSD enclosures work. Do a bit of research on Raspberry forums before making any purchases. Also, Pi 2/3/B+ sadly don't support USB 3.0 devices, so much for backwards compatibility. I bought a handful of cheap SSDs and USB 3.0 enclosures for this exact purpose, but still haven't got any of them to boot, even though I did research and supposedly bought several from Sabrent that should work. In retrospect I should have looked closer, Sabrent makes a bunch of very similarly named drives with slightly different specs, some of which apparently aren't compatible. I found a forum comment suggesting to try the enclosure with USB 2.0 cables, but that avenue has been fruitless thus far. I will probably have to order some USB 2.0 enclosures.