Is it permissible to take the interest paid by the real estate company for the down payment and use it to pay the company for apartment maintenance fees?

It is permissible to agree to purchase a real estate unit that has not yet been built if it is described in a manner that removes ambiguity. This is called an Istisna' (manufacturing) contract. If the contract is concluded, the upfront payment becomes the property of the company; its growth and zakat (definition) are their responsibility. There is no sin upon you if the company places it in an interest-bearing bank because the money has left your possession. However, it is not permissible for you to take a return from this money, as the stipulated interest would subject the lender to ambiguity, and the Prophet, peace be upon him, forbade combining a loan with a sale.

However, if the contract is not concluded and the money is merely a "earnest money deposit" (hamish jiddiya), it is not permissible for you to allow its investment in usury, and you must refrain from dealing with the company if they insist on it, because the money is yours and they are your agent. The preferable view is that it is not permissible to take what is called "earnest money" at the stage of a promise to purchase.