Has anyone used a site called truth finder to locate someone and or a persons address to mail a complaint to? Basically a previous tenant of mine failed to pay a month and a half rent plus damages, and left no forwarding address. How does one go about locating this person? I have his work address, but the issue is this person works night and wont be able to sign for the registered letter. Any info. would be greatly appreciated.

It's been a while I was a landlord. (BTW dont miss it)
Can you have the sheriff deliver the letter to his/her work?
Did he/she leave a forwarding address at the post office?
If the answer to both is no, this might cost $$$.
Try spokeo type sites, gotta do the legwork. Make calls etc, be crafty & creative if you have to.
This site looks OK:
https://rehold.com/NJ
It has "has been related to" type of hints.
You have to decide if the work is worth it.
Sometimes it's more efficient to just chalk it up to a learning experience and write it off.
Other's it's the principle.
ymmv jm.02

The Sheriff wont delivery the letter to his work due to him working from 11pm to 7am, but the clerk did state I could mail the registered letter to his place of employment but he would have to sign for it. Since he works nights he wont be around to sign.

I'll try that site and report back, thanks for the information..

Since you know where and when he works you can hire a process server to wait for him to leave work and serve him in person.

How much do they charge?

No idea, never had to use one. I don't think it's terribly expensive though. Probably somewhere in the ballpark of $100 I would guess?

If you know where he works- and he gets off at 7 am, why not sit outside and follow him home?  Get the address and you are done.

Otherwise, you get a process server or a licensed Private Investigator for less than $250 to serve it or tell you where he lives!