And some retirees might relocate more than once during their retirement years. Some follow their grandchildren through several moves, White says.
"I see many retirees who move more often than younger people," White says. "For younger families, they usually move to an area with a good school district and try to stay there for a while. With retirees, they often move several times to be closer to their grandchildren and family members, and relocating costs money each time you do it. You have to plan for that."
Sure, they're easy to spoil, but doing so can be costly. As Kaplan says, many retirees spend more on their grandchildren than they expect. This includes setting aside money to help their grandchildren cover the costs of college tuition. This can be an especially high hidden cost, depending on how many grandchildren retirees have, Kaplan says.
"You don't want to give one grandchild money for college and then not have any left when the other grandchildren come along," Kaplan says. "That can cause a lot of bad feelings."
The best way to prepare for these hidden costs? As usual, it's all about planning long before your retirement years arrive, says Ray White, senior vice president of PNC Wealth Management in Orlando, Fla.
"You don't have to spend hours planning for retirement," White says. "The key is to get started and review where you stand at least annually."
Pre-retirees who do this may reduce their odds of being blindsided by unexpected costs in their golden years.