LOL LOL All the answers are pretty much the same, but I'll throw my 2 cents in anyway. Kudos to your brothers for looking into this and asking questions. Right away that shows the makings of a responsible pet owner

1. Do only male cats spray or do females do that too?
Actually, both are capable of spraying. Spraying is a behavior that is used to mark territory and display dominance (much like dogs). However, it is more common in males than in females.

2. Does nutering/spaying them take care of that problem?
Yes. When a cat is neutered/spayed, the instincts for mating and therefore all the behaviors associated with it will decrease significantly. Either way, it's best to get the cat 'fixed' anyway...preferrably before the age of 6 months if it is a kitten. A male cat can start spraying behavior at 6 months of age, and once they start...they won't stop. Even after being fixed!

3. Do cats shed alot?
It depends. I have 2 short-haired cats, but they are completely different when it comes to their coats. Marius has a short close-lying coat, whereas Scooter has a very thick double coat. He sheds a lot!! Some long-haired cats probably shed less than he does! LOL

4. On average for a healthy cat, how much does it cost to get their annual shots and check up?
I think Noahsmommy has the best deal ever! LOL LOL It does depend on where you take them and what region you're living in. It seems like I'm always dropping more than $80 per visit, so I guess it's just a matter of finding the right vet!

5. Dogs go on Heartworm Meds every month, is there something that Cats have to take every month to prevent something?
Not that I know of. The only thing similar would be protection against fleas and ticks for oudoor kitties, but it's better for cats to be indoor-only pets. There are lots of people who aren't too familiar with cats who think they have to let cats outside. This isn't true. If you adopt a cat and keep it inside, chances are it won't know what it's missing as long as it gets enough attention and toys inside

6. On average, how much worth of food does a cat consume per month? (I am not sure what brands are the best, but they would be interested in giving it the price equivalence of Nutro or Eukanuba)
You can get Nutro or Science Diet cat food that would be pretty much on par with the Nutro or Eukanuba dog food. Depending on the size of bag you get. I'd assume pet foods are pretty similar in cost depending on weight.

7. Do cats claw at furniture, bedding, etc... because they are bored?
No. Scratching is actually a scent-marking behavior as well as a maintenance behavior. Cats shed their nails about once a month, and scratching helps remove old nail sheaths and sharpens the nail to keep it healthy. Clawing is also a scent-marking behavior. However, if you take the time to train the cat to a post or other appropriate location, it shouldn't be a problem. Nail caps are also an option for severe problem scratchers as an alternative to the cruel declaw process.

8. How easy is it to train your cat to use the litterbox?
Very easy! They usually come that way! Simply put the litterbox out and show kitty where it is!