I want to get a rat but I have a guinea pig so here are the questions?

Never "just one". Rats are highly social animals and need to be kept in at least pairs. A human cannot provide all of the companionship that rats require, it just isn't possible.

Solitary rats are more prone to sickness and behavioral problems from the stress. I prefer having a trio. Rats are not very long-lived animals (2-4 years, lifespan can vary drastically) so if you have three, when one passes on you still have the two.

That being said it's also best to get rats from the same litter or at least similar age so you're not "stuck" with a loner for very long when their companion/s pass. 2) About how much do they cost each? The rats themselves are cheap in comparison to some other small pets.

I think I spend about $20 for each of my girls, maybe a bit less. But their start up supplies can range from $100 to over $150, most of that being the cage itself (big, well ventilated, wire cages are not cheap - if you're lucky you might find a used one, just be sure it is SAFE and BLEACH IT before use.) This does not factor in the monthly cost of bedding, food, or any additional costs over the animal's life time. Such as pet sitting if you go on vacation.

Or, since they are prone to respiratory infections and tumors, the cost of vetting. 3) How much cage space should they have each? (Or in total) 2.5 cubic feet of space per rat MINIMUM.

For 2-3 rats the minimum cage size would be around 30x18x24 inches and that can be pushing it. Right now that is what I have my duo in (used to be a trio, and when I had the third in there the cage was a good foot taller.) Tanks are not suitable. Ferret cages are okay for size, but bar spacing could be an issue.

You don't want anything with wire floors. Wood and galvanized metal soak urine and rust, rot, stink, etc. Big doors are a must. 4) How much time do I need to spend with them daily?

As much as you can. When you first get them you want to spend a lot of time just for hand taming, and after that they NEED regular companionship. Minimum one hour per day.

They are also not the kind of pet you can shut away an ignore for long periods of time, they do best in an active and stimulating environment. If you don't put the effort into them, they will be skittish and won't make fun pets at all. 5) I heard they only live 2-4 years?

Correct. Lifespan varies drastically, but on average that is correct. I had a rat pass from pituitary tumor at 16-17 months (under two years) but I have also had rats reach past three years (my most recent loss was 3.5 years old).

1. Minimum of two, three is better. 2.

Costs varies, but I'd highly recommend finding a reputable breeder that socializes their rats well. Our breeder charges around $20-25 per rat. But that is well worth it.

I too have heard horror stories of pet store rats being aggressive and biting. You want socialized rats for a good experience. Ours have never bitten.

3. They need lots of space. Check into Critter Nation cage for 3 rats.

There is an add-on available that will double the size if you decide later on. 4. They'll take as much attention as you offer.

You want to be the alpha male. Be sure to read up on care, perhaps at ratforum.com 5. Correct 6.

Train how? Some litter train, some don't. They are smart, though.

The more time spent, the more trainable. The forum should provide plenty of examples and opinions on that. 7.

(answered in #2).

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