I want to write a letter that is compelling. My realtor says he's not allowed to attach letters to offers because he can lose his license.It's legally non-binding. What Items Are Required to Submit an Offer? In order to make an offer in NYC, you'll need two documents. The first is proof that you can actually purchase the apartment. Focus on three things: State your intentions, show that you have the financial means to make the purchase and make a personal appeal to the seller. A personal letter included with your offer to buy a NYC apartment helps support an otherwise strong price or REBNY financial statement. What information do I need to submit with my offer? It's happened before where a buyer submitted an offer on an apartment that eventually ended up in a bidding war.