Okay, I appreciate all the advice here. After reading so many threads here, I thought I had everything down pat, but I missed alot...
> Once some of you mentioned it, I realized the error of not asking right up front, when they were going to move in; it would have been very reasonable to say "I don't really wish to let it sit empty for a month". Now that we've already agreed on so much, I'm uncomfortable trying to push them to move in earlier. Certainly, I don't want to re-activate the ad and start interviewing people again.
Actually, in the future, I'll put a target move-in date in the ad. They actually told me up front that their existing lease was until end of November, but it didn't mean anything to me!!
> If I had said right up front, "you can move in early, but you'll have to pay for the time, nobody would have thought twice about it. Now that I've already said "sounds good to me, you won't be getting in anybody's way", I'm not comfortable backing out. I *will* learn from experience, however.
(Wow, I can actually SEE K. Marie Poe rolling her eyes at that comment!!)
> On the checks issue, I admit I don't understand the issue... I'll have a month for the checks to clear before I give them the keys; the Lease Agreement specifies that if they bounce a check they will pay $25 plus all bank fees, and all payments after that will be cash.
(Besides, these are the tenants who want to set up auto-pay, as noted in my other posting today).
Thanks again for all the expert inputs that people have shared.