Upvote:10
There's no rule saying that people who host international guests in their home need to be employed; it is hard to see how that would factor into the decision process for a visa.
Note well that "being invited by a citizen" does not in itself make visa officers any more likely to accept the application than they would be if you were just going for a tourist visit and staying in hotels.
All the invitation does is (a) explain that you have a plan for where to sleep and what that will cost you, and (b) help explain why you'd want to go to Finland in the first place. Your friend is not vouching for your honesty or plans, and his employment status does not matter for whether the invitation is a convincing explanation for (a) and (b).
While some explanation of each of these points required, they're usually not the sticking point of an application. It is much more important to the decision what your own circumstances in your home country are, since they are what must explain why you'd desire to go back home after the visit.