Well, I'm going to have to kinda sway you away from them... But it's up to you, but males and females will almost certainly exceed 7'.
1. Males - 8 ft. - 10 ft.
Females - 10 ft - 12 ft.
2. What the feed on will depend on the conda itself, most will feed on F/t Rodents though, once a week is fine.
3. Overtime the snake will need at least a 6' long x 30" wide x 18" high cage. I would recommend plastics caging, such as Monster-Cages, Animal Plastics, Vision, etc. A water bowl that will allow the snake to soak in. A hide or *Humidity Hut*. You can throw any fake plants and stuff in there as you want, but you are going to have to clean them everytime your snake urinates or deficates (which happens a lot).
A basking spot of 90-92 degrees, and a backround temp of 80-83 degrees would be best..
4. Heating will depend on the cage, you can do overhead or belly heat. Make sure the habitat is always clean, like you would any other snake, make sure they always have fresh clean water, as they tend to deficate in their water about 70% of the time.
5. Temperment depends on the snake itself, a lot of people find Yellow Anacondas to be more tempermental than Greens... All Anacondas are very personal snakes, and if you do something they don't like, they wont really have a problem showing you. Treat your snake with respect and it might treat you the same way basically.
Anacondas do tend to be problem feeders, Greens more than Yellows, but either way... Most of the time they wont have too much of a problem going on F/t Rodents, but sometimes there are the tough ones, so if you do decide to get one, just be prepared, don't think it can't happen to you, because it most certainly can.
6. If you are only looking for cheap yellow anacondas, then that's a good sign that they aren't for you... These snakes are deffidently not for beginners, and basically with Anacondas, the higher the price (in most cases), the better the snake. I know there are a few exceptions, and this rule goes for Greens over Yellows, but still... The snake might be cheap, but I can guarentee you that housing is going to make up for it in price. I've spend well over $2000 on caging, and I'm about to spend another $1700 on more. So be aware, the price will add up one way or another.
Hope this helps some!
~Ben