I understand that freshmen is the plural, but freshman year is the first year of high school or college, there is no "freshmen year". So I could see someone wanting to build a website to possibly help freshmen students through their freshman year, but in that case they could just register freshmenstudents.com because that's available and would fit the market just as well.
Just trying to help. I think there's a limited market of end users because of the spelling.