I'm not chancing the wet lead acids in my living space. My health is worth more than that. They also shouldn't be stored in an airtight space either. I used wet cells in my last rig, and I regret not spending more money for AGM's. It was such a pain in the breeches doing all the maintenance and checking on them all the time. But opinions may vary.
The problem with going small now and just upgrading later, is that you have to upgrade later. Charge controllers aren't cheap. Buying wires and installing them can be a pain and they cost money too. Upgrading later means replacing those things. Sometimes spending a little more up front will save you some in the future. Don't skimp on wire and safety things like proper fuses and stuff. When water escapes out of some plumbing, it usually leaves a mess. When electricity escapes, it's usually a whole lot worse...
Sounds like you don't have much of a power consumption. I mean, charging a phone a few times per day is nothing. You might be good with one of those small all in one power station units and just charging it off the car when you're driving or maybe getting a small suitcase solar setup. Don't get wrapped up thinking you need some crazy system that can run air conditioning, if you're not running air conditioning. But again, only you know your power needs. We're all just speculating.
I do know I wouldn't want to use my truck-battery on any regular basis, I'm not totally ignorant on some things. No worries on me thinking something sounds condescending. If it happens, I always figure it's their issue, not mine. I know I'm intelligent, and very teachable, but at the same time, I seem to have a harder time as the years go by, staying one one track, and short-term memory loss, you know, like, what did I come in this room for 
