Find tenant for prop A before giving notice to tenant at prop B?

[Jack B.]

I'm moving back into one of my rentals this November and renting out my currently primary residence. Was planning on finding tenant for property A (primary residence) first before giving notice to tenant at property B. They are on a month to month lease, and the house looks just like I left it, so it's not going to need major anything to get it move in ready. 

What I don't want to do is give them notice prematurely since I will then be stuck carrying two mortgages at the same time by my self. Yes I have reserves, heck I have the income, I just prefer saving the money for a new deal. So I figured I'd find a tenant for my current residence first, and hopefully still be within the 20 days notice period before the end of the month.