Herb Evena, or someone who calls themself Herb Evena asked...
Before that question can be answered, I think we need to know what will the adult in question will need the tools for. For general home repairs, one set of tools will work but for someone with a desire to try woodworking, a different set of four would be required.
I probably don't need a pair of pliers to build a book case, and I probably don't need a circular saw to change an outlet.
Another question: what is your definition of a "tool" in this instance? Is a single handle with multiple inserts one tool or more? Is a 18v kit with a circular saw, drill, reciprocating saw and flashlight a single tool or does that fill the full quota of 4?