Let me give a hint how you can find refs for yourself. This type of things are dealt with in dharma sastras. Go to the most prominent one, Manu samhita, online (if you don't have in on your hard disc) and search for desired keywords.
Ms 8.396 and 10.123-5 are closest to support not using other's clothes.
396. A washerman shall wash (the clothes of his employers) gently on a smooth board of Salmaliwood he shall not return the clothes (of one person) for those (of another), nor allow anybody (but the owner) to wear them.
But that doesn't really address "karma," that just says that if an employee is washing his boss's clothes, he shouldn't give them to somebody else. That's the sort of thing that should go without saying. If I dropped my clothes off at the dry cleaners, I'd be furious if I saw a stranger on the street wearing them.
I think we create our own karma through our thoughts, decisions, and actions. If we can be condemned by something as simple as shopping at thrift store, then there's no point in even trying- I'm already doomed.
Sin spreads from a man to man slowly by conversation, mutual touch, frequent association, taking food together, sitting together, lying together and travelling together. (Garuda Purana 1.115.6)
The second Ms quote is about used clothes given by brahmanas to sudras. They are fit to wear them but there is no mention that dvijas should do the same.
Please see Bhag. 2.2.5 and purport
" Are there no torn clothes lying on the common road?"
Certainly such clothes would have been used by someone.
Personally, I gladly accept any gifts of useable preowned clothing. To me , it is terrible waste of Prabhupada's Laxsmi to buy new clothes. These funds can be used for so many other important necessities. Do one Nirjala Ekadasi fast and you can burn up more karma than you can imagine.
Yes, I agree. But if u are bit more sensitive, maybe others has this also, u can feel sometimes some really strange vibration from someone else clothes and u can be affected. The owner´s mind, frame of midn, deeds....everything is there, even if the clothes are clean.
And according Vaishnava ettiketh, what I read, that we can give our clothes to "younger" devotee and accept from "elder". Hmm..but I didn´t read about wearing the clothes from unknown people.
Nectar from Jayananda's website: Murali Krsna's account
So finally, Jayananda and I were in a store together. Jayananda spent about a half hour getting the cheapest, most funky pair of pants he could find, and he goes, "Okay, I think these are okay." Then we get in line and I said, "Jayananda, there's some flip-flops over there," those little thongs, for about 80 cents. And he had one that was about this big on his foot, it only went about halfway up his sole, it was red, and he had another real big one with a hole in the bottom that was brown, and he wore those for months. I said, "Jayananda, why don't we get a new pair? They're only 80 cents." He goes, "A new pair of thongs? Hey, I've got another month left in these things." I talked him into the thongs. So he was in line, I could see him, he was intensely meditating, he was in intense anxiety. He was looking out, I was talking to him, and he wasn't even listening. Finally he turned around to me and he goes, "I think I can do it." And I go, "What?" And he goes, "Well, I just don't think I can pay for the pants. I think I can do it with the thongs, but the pants, it's too much. I've got them on, I think I'm going to walk out. What do you think?" And I went, "All right." So he pays for the thongs, we walk out the door, and immediately we get caught. Jayananda goes, "Oh, no!"
We get in the room and Jayananda goes, "I did it. I did it, I admit it." Then the cops come, there were two cops there, and he goes, "Look, officers, I'm a monk, it's God's money, I just couldn't spend it on myself. I tried, I've had these other pants for months now. I just couldn't do it, it's too much. This ten dollars could buy three books, could feed twenty people, and I couldn't spend it on myself. I just couldn't see it." So the cop looked at the other cop and he goes, "This guy's a saint. What are we supposed to do with him?"
So they brought him in front of the judge. Jayananda explained the whole thing to the judge and the judge says, "The only penalty I can incur on this man is to pay for the pants that he has taken." And the cop jumps out of his seat and he goes, "I'll pay it! Let me pay it, Judge!" They were only a ten-dollar pair of pants. So the cop gave five and Jayananda paid five, and they squared it away finally.
Another nice example is that of Gaura kisora das Babaji. He used to go to places where corpses were burned and take the clothes lying around which were used to cover the corpses. He would wash them and use them as garments.
The only thing he did was remembering Krsna and therefore he didn't incur sin. Alright we are not to imitate saintly personalities, nor do we have to were these kinds of clothes. But we can also remember Krsna according to our capacity and wear second hand clothing or shoes without incurring sin, just as Jayananda did.