It was a family summer home in Maine from her side of the family.
From the article:
“On another financial matter, Jane Sanders said she and her husband paid cash — $575,000 — for the four-bedroom summer house they recently bought in North Hero, Vermont, on the Lake Champlain shore. She said she sold her share of her family’s long-time vacation home in Bridgton, Maine, to her brother for $150,000, added some money from her retirement account and from an advance her husband got on a book he is writing to come up with the money to buy the couple’s third home.”