"jako" is just an adverb here, so it won't decline with the noun following
thank you
Why is "modelka" in the nominative here?
That's the construction we use with professions. jako (as) + the profession in Nominative.
Wow, this Polish sentence is exactly the same as in Czech language! :-)
So is modelka used for a female model?
Exactly. A male one is simply "model".