All US senators and reps should have a residence in their home territory and DC (they need to understand their constituents' area and they need to be in DC a lot). Bernie's is a 1 bedroom in DC, so those two are a given imo and nothing to be concerned about. His third is a $575k rural lake house; probably a country retreat from being in the cities of Burlington and DC all the time. So while getting a little extravagant for the average American, it's certainly not very unusual for many people in the US to have a modest rural retreat "cabin." I've seen many blue collar families in that circumstance, even in California. And I say this as someone who wouldn't vote for Bernie.
I don't have an issue with his rural retreat, but calling Burlington a city isn't exactly conveying how quaint of a town it really is. It feels like a town I'd visit when I want to get out of my also not big city.