OK so you add a speaker and turn on google now and bam…google home. But…I think you need to be running a relatively recent version of Android to do this. I am guessing 5.0 and up? So if you got a phone that can do this…or maybe something that could be upgraded thru other means…it maybe worth doing.
https://www.cnet.com/how-to/turn-a-spare-android-phone-into-a-google-home/