That's fine for most fields. I'd try to make sure that's your last LOR -- i.e. submit 2-3 others, and leave this one for the end. If you submit 3 others, and then add this as a fourth, no one can complain at all. Remember that MSPE's don't come out until Nov 1st anyway.
Probably best to have them in by Nov 1st, Dec 1st at the latest. That being said, many programs will interview you with only 2 LOR's, so no hard and fast rules.
so if i create and finalize two LOR, pick all of my programs and submit my application Sept 2, can i then go back a few weeks later and create a new LOR and finalize and resubmit? Or should I have already created and finalized that LOR before submitting?