According to the federal government, the department of Housing and Urban Development, only .18% of the US population is homeless! Really?

That's about 600,000 people. Seems low.

Like any statistic, it depends.

Is HUD counting the temporary homeless or only those who have given up looking for housing?

Apparently, HUD has a two-page definition for homelessness.

https://files.hudexchange.info/resources/documents/HomelessDefinition_RecordkeepingRequirementsandCriteria.pdf

Given the record-keeping requirements to meet the definition, I would think the .18% number is way of the mark (too low).

is that point 18? like in 18 per 10 thousand?

In that case, yes, I believe that. They are mostly concentrated in populated areas so it may seem like more than that.

I'd like to see other statistics that account for temporary shelters for who would otherwise be homeless.

Not according to this.
https://www.hud.gov/press/press_releases_media_advisories/hud_no_21_041

Or the new NIHP report. Our the new AHAR report.

Sounds like a cherry-picked figure or a misreading of a lengthy report.

It's very believable. Lots of people just prefer to also have an illegal urban camp, right on the pavement.