Why Brooklyn?
Serious question.
for 1500... roommate or no?
if yes, he can live in Manhattan. that's why I'm asking- why brooklyn?
My guess is he is thinking he works near Brooklyn Bridge (I am guessing on the BK side), so better to live in Brooklyn.
But Floppo is right, if he's willing to have a roomie, Manhattan is in play. If so, I would look to the Lower East Side. LES is an interesting place now, it's where all the hipsters in Williamsburg came from. It has since gotten less hip, but safer, and there's a lot of cool things there. Cool shops, a lot of affordable drinking and eating options, and upscale places as well. Lots of start-ups keep office space there, and Happy Hour is very active. Late night, I would say there is a sprinkling of hipster, but the majority of the crowd is 20-something white kids, that are cost-conscious. It's not cool or up and coming, but nothing in Manhattan is. If a 28 year old is looking to make a lady friend, without popping bottles, it's the best bet.
Williamsburg, Greenpoint, and Bushwick (no further than the Morgan stop in the L) are also all in play, in BK. They are all connected, and are in various states of hipster-ization or gentrification. Greenpoint and Bushwick are very much the way Williamsburg was 10 years ago. Coffee shops, funky bars and such popping up. Greenpoint is definitely still Polish, but is also definitely hipster. A major detriment to Greenpoint is the subway access. It's a hike to the L, and the G is not worth mentioning. Bushwick isn't 'there' yet, but it's close. I am in the nightlife industry, and we were looking at a spot right at the Morgan stop that's gonna be a huge...complex, for lack of a better term, with a live music venue, massive beer garden, nightclub, and at least two restaurants. If you're on the Morgan stop, you are in Williamsburg, circa 2002.
Williamsburg has blown up in the last few years. I left town for four years, and going back there blew my mind. There are a lot of hipsters still there, but there's also upscale joints, unpretentious restaurants by young chefs, and lots of affordable drinking options. A 28 year old dude, first year in NYC, is gonna love Williamsburg. As a neighborhood to hang out in, at this point, it's probably underrated.
I haven't read Fort Greene yet, but he should take a long look there. Has a lot of the nightlife options, and all trains wind up there. Great neighborhood to live in if you wanna explore the city, because you can get anywhere in Manhattan easily. Also works better for his work location than any other neighborhood.
I don't know much about Prospect Park, I bow to Otis on that one.
Quick word about hipsters: Being in a bar surrounded by them, you could do a lot worse. A LOT worse. I don't spend much time in them, because I am very much single, and I don't like the hipster girl look. But when you are in Williamsburg, at some bar/coffee shop/skate park, you are guaranteed two things: Cheap drinks, and no bros looking to take a swing at you. And usually pretty cool music (obviously subjective). You know who makes fun of hipsters? Recently graduated Frat boys in Murray Hill, wearing khakis, getting girls drunk enough to make a mistake, and screaming along to Bon Jovi at 2 a.m.
I make fun of hipsters as well, and get a little queasy when I am in a Williamsburg coffee shop, but here's a little secret for your friend: Almost everyone is awful. Wall Street guys at bottle service clubs, bros doing shots of Fireball at sports bars/nightclubs, basic bitc**s that can't put there phones down, and some pretentious waxed mustache on 20-year-old fixed-gear bicycle. They are just different kinds of awful.
Anyway, in general terms, I always recommend paying the extra bucks to live in a more convenient location. Getting a better or bigger apartment for less money, just a little further out of the way, is gonna wind up costing him more money. He's gonna be out, gonna have some drinks, it's cold, and he's not gonna wanna take a train, and a 10-15 minute walk to his place. He's gonna take a cab, and $30 cabs add up. Pay the extra hundo a month to live in LES or Williamsburg or Fort Greene, and who cares if it's small.
He's never gonna be at home anyway.