You can buy in nearly any age restricted community.
Find the location and property you want and buy at todays price.
However, you can not LIVE there until one of you,or both meet the age requirements.
You might consider renting to 'pay the way' until you are ready to move. You must check the community lease/rent rules.
If that does not align with what is possible, you need to start looking seriously, three to six months before the 55th birthday.