Where to get a physical address? In US

I have a ton of information about a person (real name, fake names used in past, emails used, addresses, paypal accounts, messenger and message board names, ect.) but I need to know their latest physical address to send them paperwork. How do I find the correct address to send a certified letter to in the state the person is in?

I remember last time my lawyer charged me for this and I am trying to do this all on a budget.

TIA