rubylady you can check the gender of Charlie if you can manage to get a look at her rear end. Get down to her level & if you can see 2 holes close together, then she's a female.
All cats want a comfortable, warm home to live in, & company, so just giving her shelter won't keep her warm enough during the winter.
You'll need to take her to the vet, in a cat box, for a check up to see how well she is. The vet will worm her & de-flea her, if necessary. Older cats, generally, don't need as many vaccinations as younger cats, but ask the vet what's best. She's probably eating loads because she has worms.
Get her neutered or him castrated a.s.a.p. Female cats can start breeding as early as 3 months old & can produce more than100 kittens in a lifetime - yikes!
If she scratches you, you shouldn't need a tetanus. I was bitten by a stray cat, who I was helping to save a few years back, & was advised by the vet to have a tetanus, but a scratch isn't serious.
I'd suggest you call a local cat rescue near you to ask if they can take her on. It's a myth that cats are less needy than dogs. They suffer from many ailments, especially as they age, & can require a lot of veterinary care. My old boy is back & forth to the vets with hyperthyroidism, mega colon & other issues.
I don't mean to deter you from helping Charlie, but it is a big thing to take in a stray cat. All of my cats over the years have been strays, & I wouldn't change that, but cats need love & medical care aplenty.
Good luck & hope all works out for you & Charlie.