My body is host to millions of bacteria. Some people host a malformed conjoined twin. You can host a tapeworm in your intestines. One boy recently played host to two spiders in his left ear canal. Ever had ants in your pants? When it comes down to it, the human body is a wonderful place for things to live and grow. It is a veritable ecosystem unto itself; vast swaths of unclaimed real estate just waiting for tiny farmers, merchants, religious zealots, and soccer moms to come and make it their home.
And really, should it be any other way? After all, don’t we humans colonize every available patch of land, water, and air? With any luck we’ll be living on the Moon within the next 25 years. Why can’t our bodies be the same to other organisms?
My problem, and I suspect the problem facing many of us, is how to best monetize all that real estate without affecting your way of life. Suppose Avian Flu wants to pay you a monthly fee to live in your lungs. No problem, you say, but after a couple of days you’re not feeling so good. Avian Flu is actually stopping you from being able to perform necessary daily tasks, like keeping meals down and leaving your bed. Turns out Avian Flu, while a good renter, is not so good at co-inhabiting your body. You then have to kill Avian Flu. While that may be a doctor’s opinion, it is not good for your bank account.
I suggest you find organisms that don’t keep you bedridden or kill you outright. Tapeworms, mentioned above, are good in moderation. Just make sure they don’t plan on starting a family in your gut. Flesh-eating bacteria is a bad idea, as is Ebola, the plague (or “Black Death”), and large land mammals (elephants, bison, giraffes, etc). Look at the renters’ history with other people before signing them to a lease.
Remember: your health is your most valuable asset. Don’t let an easy payday get in the way of a long, happy life.