1. A good starter brand (inexpensive or not, height is a plus)
I've always been a fan of Fantasy Doll as a starter doll. Their 1:3 dolls are really cute. They also come in about 6 different resin colors, which means you can hybrid them with other companies pretty easily.
2. Care and maintence
Pretty much what everyone else has said. Resin will yellow, this happens, it can be slowed... but, it's gonna happen. To slow the process, keep out of the sun. Magic erasers are made of pure compressed magic and are something that should live in your doll-kit.
Other thing that should stay in the doll-kit is a couple of sets of hemostats/forceps. These are used to clamp elastic. I also use them to help tug dollieh shirt sleeves through jacket sleeves.
3. potential products i need to start hoarding for proper face ups
List of recommended face-up supplies.
4. stringing.....what is that about
It's the elastic inside the doll. Normally the stringing goes wrist-wrist and ankle-head-ankle. A less common form of stringing is wrist-wrist, head-waist, and ankle-hips-ankle, but the doll has to have been specifically made for that type of stringing; like some Unoas and the Fairyland Littlefees.
I've also seen stringing where the elastic for the arms is also attached into the head. That is usually done when there isn't enough tension in the arms and person doesn't want to have to unstring the doll, tighten the elastic, and then restring. By attaching part of the elastic up into the head, this automatically gives more tension. Granted, you don't really want to do this with crappy elastic.
5. posibility
Depends on the doll, body-type and the elastic in them.
<3
-Kiki-chan78.