I saw an advertisement for a used sofa and called the number. The seller told me that someone else had already called but he will give it to the one who arrives first. If I get there first is there an issue of Oni Hamehapech Becharroroh?
It is permitted, since it is only classified as Oni Hamehapech Becharroroh if the seller has already made an agreement with the customer and just didn’t make the final kinyan. However, if the seller did not commit to the first customer the consensus of opinion of the Poskim (Choshen Mishpot 237) is that one is not in violation of the prohibition of Oni Hamehapech.
The Perisho mentions a custom to refrain from attempting to purchase an object when another person would have bought it had the second person not intervened. It is possible that according to this minhag there would be grounds for being stringent. However, it would seem that even this custom would not be relevant in our case since it is by no means clear that the first person would have bought it – no-one had yet seen the sofa and often people who express interest in such a purchase do not come through in the end.