Contrary to the popular myth - there is NO age limit on modeling. Turn on the TV and watch some commercials - pick up a few magazines - there are models of every age range and body type in use today.
Height really is only an issue if you intend to be a Fashion model. In New York, most fashion models range from 5'10" to 6' - that's it. The exceptions are the girls with the extremely unique looks.
In smaller markets like Chicago and Philadelphia, 5'8" (occasionally 5'7") is generally accepted for fashion. So if you are shorter than 5'8" or 5'7" - don't waste your time taking lots of pretty fashion pictures for your portfolio - stick with commercial looks.
Do I need to be really skinny?
Fashion models still tend to be very skinny. Commercial modeling doesn't require that you be "skinny" but you MUST be in good shape and well proportioned.
The key is to take care of your self. Don't over eat. Do eat well balanced meals and avoid the snacks. Do exercise and keep yourself in good shape.
If you are overweight - you are just kidding yourself - you won't get work.
