Parents need 192 sq ft of subfloor and carpet changed. Cost for someone to do this ?

So in my parents living room, the floor has a ton of soft spots and it needs to be changed out. My dad's too old to tackle, I can't even use a hammer properly so what would be a reasonable amount for someone else to do the work for them? It's a plywood subfloor, joists and posts are fine and they're going carpet over it.