If you're planning your retirement, I'll hazard a guess that your future housing arrangements aren't your primary concern. And I don't think anyone is eager to think about what sort of living arrangements they'll need when they're 85 years old and a little less spry.

All the same, you need to consider what sort of home you'll retire to. Here are the three factors you need to take into account.

1. Mobility 
When my grandparents moved closer to my family nearly 20 years ago, my grandmother was pushing 70 years old, and my grandfather near 80. They inexplicably purchased a second-story apartment -- with stairs. Of course, the end result was a difficult, drawn-out, and exhausting move after the stairs became unmanageable and downright dangerous.

Reduced mobility is a reality for nearly every retiree. About 70% of people over age 65 are expected to need long-term care at some point, which means you should prioritize making your home as easy to live in as possible under a variety of circumstances. It's an especially important consideration if you, as my grandmother put it, "would rather die" than live in a retirement community.

You need to plan for loss of mobility early -- before you downsizing or get that flat in Miami. Ground-floor apartments, accessible parking, elevators, and proximity to stores and medical facilities are your friends. A loft apartment with an artistic but slippery staircase, on the other hand, is not. 

2. Maintenance
I get it: You love your four-bedroom house. I would too. If my parents ever sell the house we grew up in, I'll be an emotional wreck. Yet I'll probably encourage them to do so.

The fact is that a big house is a lot to manage, both physically and financially -- especially for people who are in their 80s. Think about cleaning (you may need to hire a cleaning service at some point) and repairs (pipes burst, and roofs leak). These costs come on top of all the usual fixed expenses that go with home ownership, not to mention your mortgage if it isn't paid off. 

Downsizing, on the other hand, reduces these headaches. One study found that moving from a $250,000 house to a $150,000 one could save the average person over $6,000 per year. That's an extra $500 every month for travel, recreation, or other expenses. 

Downsizing to a rental is also an option -- and quite a great one if you're looking for convenience. If you live in an apartment, things like the roof and the plumbing cease to be a concern. Cleaning is simpler and cheaper. You'll also save on property taxes, and utilities will almost certainly be lower.  

3. Location
If you do decide to move, be strategic about where you go. 

My grandparents' move to our area proved a wise decision: My parents, living just five minutes away, were able to ensure that my grandparents had all the care and attention they needed throughout their golden years. 

So, tempting as it may be to move to the south of Spain, think about it carefully first. You'll likely be more and more reliant on others in your later years, so you'll want to have people who can help you nearby. If that includes hired help and you can communicate easily in Spanish, then your plan to relocate to Malaga might be perfect. But if you long for the comfort of family in times of stress or are far from bilingual, then it might not be a winning choice.

Talk to your spouse and family about what kind of help and assistance you may want and consider the best places to get it. Where will your health care dollars go furthest? Where will you have the most attentive family members?

Discussing these issues now, rather than the moment they become mission-critical, will save you a whole lot of turmoil and make it easier to transition into a peaceful and dignified old age -- an old age, in other words, that you can enjoy.