Q.can any hibiscus stand winters
A man up the street has 3 huge hibiscus plants and he said he doesn’t do anything to them in the winter. We live in Iowa so it gets darn cold. Could he be telling me a fib or is there a species that withstands cold and doesn’t need to be brought in during the winter?

Yes, there are cold hardy hibiscus. These are different then the tropical varieties.
Here are links that have more information.
https://www.gardeningknowhow.com/ornamental/shrubs/rose-of-sharon/blue-hibiscus-information.htm
https://www.extension.iastate.edu/newsrel/2002/aug02/aug0242.html