I'm thinking the same thing as Noodles, how do you know this bird has a "birth defect' and not something like an Avian Viral Disease, or a bacterial infection, or some other condition that is either going to eventually kill it or cost thousands to treat? Any time I hear about a parrot with a medical/health issue and someone says that it's 'a birth defect" or it's "congenital" I cringe...And usually they haven't even had it to an Avian Vet, they're just guessing that it's congenital...
If we can ask, where is this Jenday Conure that you've been looking at, at a pet shop, a breeder, or is it being re-homed by it's current owner? How old is it?
If it's being re-homed by it's current owner then you really have to question what is actually wrong with it, because people unfortunately will say anything to get rid of their pets and make some cash...It's disgusting but it's true...
And if it is actually some kind of orthopedic issue that it was born with and it has issues perching and it falls, that means that there are many other issues it also has, like standing, eating it's food (can't hold anything), possibly flying/landing, etc. So it's going to be a challenge for anyone...That doesn't mean you can't do it, but if you've never owned a bird before at all, it's going to be a bit tougher. If you're up for the challenge and you're willing to find a Certified Avian Vet (no "Exotics" Vets, must be a CAV to deal with an issue like this) and take the bird to the CAV immediately after bringing him home, and you have the money to take care of any other issues that they find after doing a complete Wellness-Exam with Blood Work, a Fecal Smear, etc., then if you think you can give it a good home and can afford to support a special-needs bird, then that's fine. But without knowing more about this bird and it's history, there's a good chance that you're going to end-up getting hurt, just like the poor bird...