The missing word is "deposit." A deposit is a payment. Typically it means a part of the price, but paid immediately, in advance. You aren't going to rent the house until July, but you are paying a deposit right now. It often is counted as part of what you pay, but you pay it right away to show you are serious and interested. To "close a deal" means "to reach agreement." Let's say you are buying a car. Salesperson: Our price is $25,000. You: How much will you give me in trade for my old car? Salesperson: $10,000. You: I'll do it if you give me $11,000 for my old car. Salesperson: I want to close the deal. I will give you the $11,000 if you will agree to let us do the financing. You: OK. At the moment when you have both agreed--and, in the United States, traditionally, shaken hands--the deal is "closed." Finalized. Completed.

Hello, the expression ‘to close the deal’ means to make an agreement official. For example, if you wanted to rent an apartment, you would pay your deposit and sign a contract. It is at this point that you may say ‘I have closed the deal.’ Hope this helps!