The body of the missing Fairfax, VA firefighter was found yesterday in Shenandoah National Park. Sounds like a suicide. Was it?

It is doubtful that it was suicide. Only the coroner's report and potential police investigation may reveal the likely cause. It is an open investigation, with much of the evidence withheld from the public, like normal, standard procedure. Just like everyone else, you will have to wait until the investigation is closed, and even then, you may not know, because the news rarely reports non-sensational portions of the story.

A quick search online and there is lots of information, however until the coroner gives their verdict nothing including media reports will be accepted

"Officials also revealed that a suicide note had been found in her car.

"The physical and digital evidence collected during the course of this investigation – to include a note recovered from her car – leads investigators to believe there was no foul play involved in her death," Virginia State police confirmed in a statement."

how would anyone know at this point? and why does it sound like a suicide?

This has nothing to do with renting or real estate.