It has nothing to do with age - it is all about how much gain a person or a couple filing joint can exclude from the proceeds. Remember when a person determines gain, you use the cost of the home + all the improvements, repairs and standard maintenance to determine your cost basis. Subtract that amount from what the house sold for less sales expenses that gives you your gain - then subtract the sell of personal residence excludable amount shown in this link -
$250,000 or $500,000 depending upon the tax filing status.
IRS Topic No. 701 - Sale of Your Home
BTW, the excludable amount is cumulative so the excludable amount is for a lifetime in case you buy and sell more than one personal residence in a lifetime.
It's Always Something . . . . Roseanna Roseannadanna