What Do You Feed Spiders?

My friend is migrating to another country and he asked if I would be willing to take care of his tarantula. I haven't answered him yet because I still have to consult my husband. We have kids in the house plus a dog and cat so I do not think he will agree. It is interesting though and will try to convince him. We can just put locks in its aquarium/container. It made me wonder though what pet spiders eat. Where will I get spider food? Do I have to give the spider live insects or something?