Yep, its a bad idea to let your potential new boss know you live with your folks.
I'm sure its the combination of stigma and the boss wanting you to be actually desperate. If your rent is low, you're not going to appear very desperate. If you don't have a wife, kids or car to take responsibility for, you're not very desperate. If you're not desperate, you'll have the option to jobhop without fear quicker.
I've been thrown out because they didn't like me regardless whether I did a good job and I've been thrown out in a combination off 'You're not from the right school and you live with your parents'. It's disgusting and I've been jobhunting for nearly a decade now, they can do this thanks to daily contracts.
That is, indeed, disgusting.
I understand that they do this because they want to feel superior, they want you to depend on them and it makes them feel better (probably that happens because they feel like they're a lot inferior to everyone else and they need to feel something else), but still, that's sad.
I was lucky enough to start working online since I was 16 and when I finished high school I started working on the Internet immediately. I didn't have to go to a normal job, but I saw a lot of people having to do that and it wasn't nice.
They had to work a lot more than me, and for a fairly low amount of money, while being treated like crap. Not worth if you ask me, but there's nothing you can do when you need to survive, especially when you have all kind of responsibilities.
I don't know in how many places you'll get fired for living with your parents, but it really suck that it happens anywhere. It's sad people like those exist and they even have high functions. They treat everyone bad and then they wonder why employees aren't motivated to work more.
Life can really suck sometimes.