On some of these lengthy explanations instead of type. Here's a better effort on my part:

When you close a mortgage, you pay your interest in advance for any partial month, so unless you close on the last day of the month, you pay the balance of the month's interest in advance, at closing...more money up front.

In this example, he closes on May 2, so he will have to pay the mortgage interest from May 3 to May 31st with his closing costs - up front, before he moves in. Sometimes needing that extra money up front (instead of closing on April 30) can cause problems.

Mortgages pay interest in arrears, meaning after the fact. So the mortgage payment you paid on April 1, is really March's interest. So, in this example, because he pays his May interest in advance with his closing costs, his first payment, which is due on July 1st, pays the June interest plus principal.

So, when you close in May, there is no payment due on June 1st (because you paid it with your closing cost) and your first principal plus interest cost is due on July 1st. While you can think about it as a skipped payment, most 1st time homebuyers, if their close date shifted from April 30 to May 2, it means they will need more money at close (to pay for May's interest in advance). That is what I was trying to warn him about.

Also, although it says your due date is the 1st, your payment isn't late until the 15th, so you shouldn't pay early, especially if it is an electronic payment - I would pay on the 10th instead of the 1st. Gives you more time.

Hope that helps. I was too brief before.