"So, like, what do you paint?"
Give people some credit here. For the average person, painting is such a challenge that they can't imagine what it would be like to make something with a paintbrush.
So tell them about what you paint, but don't get weird. i.e., none of that "I paint my soul" stuff. Stick to nouns that we all know and understand and you'll do fine.
"Do you make money?"
Ah yes. Money. Tell them the truth. And leave it at that. Or if you're in the phase where you haven't made a dime yet but you're working hard, say you're in "the investment stage" of your career. You're welcome for that.
"Art is useless!"
Here is the true challenge my friends. Stay calm. Don't start ranting. Breathe.
Fun fact: anyone who feels this way is not your audience. You're not making art for them, so don't worry about it. Find something else to discuss. They're probably cool, they just don't like art.
"Will you ever go get a real job?"
This one stings. Just remember, by the very nature of your career choice, you've excluded yourself from some people's "responsible people" list. You're just not going to be able to end every conversation sounding impressive, together, or even smart to some people.
Fact is, some people think art is dumb and that artists are even dumber. Their stance is that you cannot succeed, and that even if you do, you'd be better off working a "real job" and making "real money." They aren't your audience either, so be polite, and find something else to talk about.
"How much does this one cost?"
Just tell them. Don't hem and haw, don't "cut them a deal" (unless they're your mom or something). Just tell them the price, and have prints available if they aren't looking to spend real money. It's hard to spit prices out, I know. But you can do it.
That's all I can think of my friends.
Stay calm out there, and keep making stuff.
If I missed any common questions, let me know; I like to know I'm not the only one suffering through awkward conversations about my life.