Just had a question answered by Quinn F, so I'm feeling optimistic.

I'm looking for info (hopefully a title) on another obscure 80s movie. Younger teens, not yet drivers age I think, maybe about 12 years old, a dark haired girl (shoulder length, bangs, nearly black) moves or visits a new place. Large house. Scary appearance. She and some other kids find out about a mystery (maybe a missing person or buried treasure), something and start looking. Some scary moments. There are tunnels under the house (and surrounding area?) in the end they find a dead body (really just bones and clothes) in the tunnels and find out one of the adults killed the person (a woman I think). Anyone have any ideas?

Sounds like Mystery Mansion

Holy crap, how did you do that? That is it exactly! Thanks again.

You're welcome :)