http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3481923/

In "SIDE EFFECTS RELATED TO SEXUAL FUNCTION": "The side effects were completely reversible in 5 days when the medicine was discontinued" and you'll also notice that, funnily enough, worrying about getting side effects increases the chane you will actually end up with side effects...

And in "http://www.the-dermatologist.com/content/does-finasteride-lead-permanent-sexual-side-effects": "Potential side effects include decreased libido and disturbed sexual function, but the majority of research shows that these sexual side effects are reversed when the drug is withdrawn."

Now it is worth mentioning that yes, Fin can cause permanent adverse effects in addition to reversible side effects. There's even a foundation dedicated to that, and you can read their research here: http://www.pfsfoundation.org/published-research/. It is also worth noting that side effects are rare to begin with (2% of all Fina users, according to one of those links) and permanent sides even rarer.

Now I know that the plural of anecdote is not data, but here's my personal experience. At some point, I had been taking cyproterone acetate for 5 months. If you don't know about it, Cypro is an anti-androgen that is massively more potent than Fina; it does not inhibit 5-alpha R, it completely wipes out all testosterone (and thus DHT) from your system. Now the side effects I experienced were what you'd expect them to be: complete loss of sex drive, complete erectile dysfunction, azoospermia, oh and I ended up with C-cups. Once I stopped taking Cypro, everything slowly came back to how it was before. This was from an antiandrogen hundreds of times more potent than Fina, so if you do get sides on Fina they are reversible if you quit soon enough.