Some employers will pay the cost to get a security clearance. Others will not. IME, employers will tell you in the job description which kind of employer they are.
"Must have a currently active $TYPE clearance." and "Must be eligible for a $TYPE clearance; position contingent on acquiring a $TYPE clearance." are the sorts of phrases to look for.
"Must have a currently active $TYPE clearance." and "Must be eligible for a $TYPE clearance; position contingent on acquiring a $TYPE clearance." are the sorts of phrases to look for.