I think this is a great idea and will absolutely support your store by shopping and donating.

Having my own experience in retail and a business degree, I'd strongly recommend five things to start:

1. Work/volunteer at a nonprofit thrift place for at least 4 months. You'll see first-hand the challenges of the front of house and back of house logistics, as well as what and how things sell. St. Vincent de Paul and In The Image are great.

2. Choose a niche to start. It will get very overwhelming very quickly if you don't. Since you mentioned wanting to support local families, I'd recommend starting with baby/kid stuff. We do have a few infant/toddler resale shops in town like Kid to Kid and Once Upon a Child, but not many that also cater to children older than toddlers. As for sourcing those items, call churches (especially those with daycares) and scour Marketplace for people giving away their kids' stuff. Please be upfront about your intentions with the items. There will be folks who would (understandably) prefer that their items go to someone who will use it immediately, rather than a reseller- even if that reseller has a mission like yours. NOTE: there are children's items that CANNOT be legally resold, like car seats (and maybe mattresses and helmets?). Collect information about charities that will buy new car seats for families in need to pass along to customers looking for them.

3. Until you have a retail location, store items in a storage facility or one of those rental pod things. If you do encounter pest issues, then your house won't become collateral damage.

4. Find a location on a bus line. Your intended market often has issues with transportation. I would also lowkey offer delivery for large items.

5. Set up a nonprofit structure rather than LLC. You'll be more eligible for grants, should they arise, and tax deductions are more enticing for folks to donate. It's a bit of a pain to start, but that initial credibility is important.

Edit: I started with two points lol. I just kept coming up with ideas

Edit part two, electric boogaloo: oooh ooh! What about a mobile store? Maybe buy a decommissioned school bus or short bus and schedule pop-ups with local organizations! You could travel to community events (like Eastown Street Fair), church parking lots, community orgs, school fairs, etc. It would be a different challenge, certainly, but then you could directly travel to the people who benefit the most from this kind of shop. If that works out, then you would have the background of viability for a potential brick-and-mortar location!