Can I gift money to my child for building an addition for me to live in

[DoninGA]

Sure.  You can gift any amount to anyone you want to.

The individual receiving the gift does not report the gift on a tax return, regardless of the amount received.

The individual giving the gift does not report the gift given on a tax return.  However, if the gift given is greater than $15,000 for the year, the gift giver has to report the gift on IRS Form 709.  There will not be any taxes owed on the gift if the total amount of gifts ever given is less than $11.18 million.