Daddy Long Legs has a rush for I think $30, details are on the website. They are also on Goldstar for $20 (or $40)+$10 fees sometimes, I don't know about recently.
To the OP: also join LincTix if you're in that age group (21-35), it's similar to HipTix. 2nd Stage also has a 30under30 like MTC. I like Playbill's overview over all the Off-Broadway ticketing policies: click.
Besides that, if you are able to do the rush lines in the morning, that's usually the cheaptest way to get Broadway tickets. And since you're in the city for a whole month, you can also enter a all the digital lotteries every day until you win. Enter several a day, you should win one or the other pretty quickly. If you have a friend who can enter as well, even better.
You could also sign up to the willcallclub newsletter. They'll send you invites for comps sometimes (very rarely but doesn't hurt). Their annual membership fee is $20 but you can get the newsletter and invites for free and only sign up the first time you get tickets, if ever. Also get an account on showscore and rate at least 10 shows, they'll start sending you invites for a ton of obscure Off-Broadway (and possibly Off-Off) shows for free.