Im looking at some snows and saving a little.
Hankook snow tires 195/55 R15 on aftermarket rims
gentlemen ran them on his 2008 fit
I am aware I'll have to get 2 more 15" wheels and tires
thanks in advance.

 

Most likely, but you're missing two or three important variables. Width, offset and center bore. Since aftermarket than most likely the center bore is larger than the Fit's 56.1mm?

I'm guessing if it's a 6" wide wheel anywhere between 35mm to 45mm offset will work? Biggest concern if a shallower 35mm or smaller offset would be distance to the strut. Fit has small brakes so I wouldn't be concerned about caliper to wheel clearance like if it was a car with Brembo's or something similar.

Really, if you buying used bring your jack, torque wrench and test fit one on your car. If the owner refuses to allow you to test fit one wheel then walk away