Contrary to popular belief, tarantulas are really not deadly; in fact, there are no known instances of anyone dying from a tarantula bite. In addition, most of the pet store specimens that you’ll encounter are exceedingly docile, and will generally not bite unless they are severely provoked.
The most common variety available is the Chilean rose hair tarantula (Grammastola rosea), which is notoriously gentle and easy to handle. It is also known to have fairly mild venom, and almost never bites. Other docile and readily available species include the Honduran curly hair tarantula (Brachypelma albopilosum) and the Guyana pinktoe tarantula (Avicularia avicularia).
Unlike a dog or a cat, these animals do not require much care. They can go for weeks without food or water, although regular care is still recommended. They do not generate much waste either, and so cleaning their cages is easy as well.
Some species do have rather specific humidity requirements, but the most common pet store varieties are not so demanding. They also require very little space, and most of them can be kept in plastic shoebox-sized containers. Make sure that their lids fit tightly though, since these animals can be quite good at escaping.
Beware of its bite!
I do recommend reading up on tarantula care, so as to learn the proper care requirements for the specimen that you choose. Be aware that some species can be quite aggressive, and are not recommended for beginners. These species are less commonly available though, and are generally obtained via mail order. If in doubt, start with a Chilean rose hair, as this is an excellent beginner species.
Owners should be aware that even within docile species, there can be some individuals that are more aggressive than others. In addition, there is always the possibility of an allergic reaction if you are bitten.
In theory, this could result in a potentially fatal anaphylactic shock, although I am not aware of any circumstances in which this has actually happened. For these reasons, new owners should learn how to read a tarantula’s body language, and should stay away from species that have a reputation for biting without provocation.
Also, do remember that you never have to actually hold the tarantulas–just as you never have to actually hold your aquarium fish. I recommend reading up on handling techniques, so that you can move the animals around without having to touch them. This can be helpful for those who are squeamish, or who simply wish to be cautious. When in doubt, err on the side of safety.
If you’re not intimidated by the prospect of keeping one of these wondrous creatures, then I recommend them highly. They can be quite addictive, and they never fail to entertain.