You take a chance of sorts with any used car you buy. And you still take a chance with a new one. I wouldn't have much fear of owning a second Gen Prius with average yearly mileage, unless the car was only driven in Death Valley or Phoenix. Extreme heat is not a friend of batteries. If your friend is that worried about battery life, go for a Corolla. Can still get good MPG with a car that has demonstrated longevity and reliability, just like well maintained Prius have.
I have a 2006 model that's just over 150k miles. They seem to be quite reliable but I did have to do some work on the car. Here is the list I've done to my 2006. 1. water pump leaked (at around 117k) 2. rear shocks leaked (at around 117k) 3. engine makes ticking sounds (still going on at 150k) 4. HV battery replaced under warranty at (149k) 5. Catalytic converter just failed at (153k), no longer under warranty 6. Engine burns oil at about 1 quart every 1500 miles average. Other than that, the car runs pretty good. The problems I listed are pretty common for Prius cars with 150k miles (not the ticking engine). Any one of those issues can creep up on you
Our 2005 had 145,000 miles on it when we traded for the 2011. No oil consumption, no leaks. Only problem we had with it was eating rear tires at a faster rate than normal through it's life with us. Not typical for us, since we drive fairly gently and have always gotten maximum miles from tires. Toyota service and alignment shops could not find the problem. Other than that, it was in excellent shape. It did commuter service and quite a few long trips.
