If you want auto focus, you need one of these adaptors:
There are cheap ones and a much more expensive one, Metabones that costs almost double what I paid for my NEX-5T.
You can check it here: <click here for link>
Then, I personally tried this one:
<click here for link>
Cost me $90 (compared to $399 Metabones), and auto-focus was almost the same as the Metabones.
You can check how it performs here: <click here for link>
AF performance was too slow for me, so I decided to sell it and just got myself a manual focus adaptor for $9: <click here for link>
For manual focus adaptors, aside from losing the af, you also lose the ability to change the aperture of the lens. That would be another thing to consider.
So, it depends on what kind of photography you'll be using it. Obviously, the af adaptors are not a good idea to use on moving subjects, but for stills and portraits, they're not bad at all. You'll just have to decide which one suits your needs. If you can live with manual focus, then you could save a lot of money and just invest it to something else.
Good luck with your photography.
-- edited by chauza on Jan 15 2015, 07:03 AM