I would like to submit a manuscript which has 5 co-authors. But one of the co-author is presently not working anywhere. So what could be the affiliation of this author? Is it Okay, if I provide the author's last affiliation address?
Check and see if the author's last affiliation consents to being cited as affiliated; if so, I don't see why it would be a problem.
If not, then simply list the author as "Independent Researcher" and provide home address. Or leave field blank. There's no requirement for an affiliation for academic papers.
If this is not forbidden by the former affiliation, one of the possibilities is to use the affiliation where the work has actually been performed ("The work was performed when the author was at XXX"). Or it could be "Formerly at XXX".