HM! Crypto mining isn't fun like you said if you haven't tried it before, you said you are a newbie so I'm suggesting you have zero idea about the whole thing, I've seen many saying same thing until they later found out it's not for them, find motherboards specifically for mining on any stores online but make sure you start with one GPU first, use this to find your real taste in mining, maybe you will end up liking or hating it that's why I suggest not to go too deep now.
That's right, especially with PoS on the horizon. Maybe the OP should wait for a few months for a GPU price crash, then build a rig cheaply.
As for mining motherboards, I mostly stay away from them. I've had bad experiences with low component quality, not supporting as many PCIe slots as were advertised, and other issues. Just buy a regular $120-$150 Intel gaming MOBO + a Celeron with integrated graphics. Buy a 4-in-1 USB PCIe adapter or two, as well as 2 M.2 riser cards. You can easily connect 9 or 12 video cards. Plus, the resale value could be higher if mining ever crashed. I also don't like the Octominer-style motherboards which have x16 PCIe slots built in. Too much power flows through that board; I like separating the video card current from the MOBO current.