First of all, all living things can carry Salmonella.
The age of the animal does not matter.
Proper hygiene will prevent these illnesses. Wash your hands before and after handeling them and you will be fine. Keeping the enclosure clean is extremely important.
I have kept just about everything in the past 15 years. If you're into lizards I'd suggest researching these:
Bearded Dragon
Veiled Chamlelon (Very cool, as are all True Chameleons, but you must research first and be prepared to maintain them properly otherwise they'll die.)
Uromastyx
Water Dragon (Good alternative to an Iguana. Similar look, smaller size)
No matter what you choose, please research the hell out of it first. Impulse buys are common and irresponsible. Many times people will buy a new animal because they fall in love with it on a Saturday and 3 months down the road, the animal suffers because you've lost interest, and you're out a couple hundred bucks. Obviously the animal suffering is worse than the money involved, but sometime people dont realize how much money they actually will have to invest in these animals.
If you any questions on pretty much anything, don't hesitate to ask.