You can try some free e - book platforms like Project Gutenberg. Although it may not be specifically focused on'steamy' stories, it has a wide range of classic literature that might include some passionate tales. Another option is to look at some independent author blogs where they might share their short stories for free.
You could also check out your local library's e - library resources. They often have a collection of short story anthologies. Some of these anthologies may contain stories that are full of emotion and passion, and borrowing them from the library is completely free.