The law of one who enters into his fellow’s property

May I offer a business to buy from me at a cheaper price, or even at the same price but I persuade him for some other reason?
And may I suggest to him that he buy together with me, for example, from another manufacturer (and to clarify the last question I will explain: I am not a licensed business; I am only sixteen years old and I want to buy fish wholesale, but most fish farms {ornamental fish} do not sell without issuing an invoice, so I want to bring another store into the picture). Or is this perhaps forbidden because I am “entering into my fellow’s property,” meaning the importer or the fish farm from which he has been buying until now?

Shalom u’vracha.

There is no prohibition against initiatives to lower the price.

Except for a case (rare in our times) where there are not enough customers in one place for two businesses of the same type.

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