I was curious, so I Googled. This is what came back,
In New York City, practicing massage therapy without a license is a Class E felony, which can lead to up to four years in state prison, criminal fines, and a permanent criminal record.
Legal Penalties
Felony Charge: Under New York Education Law 6512, doing any professional work without a required state license is treated as a felony (the same level of charge regardless of the specific profession).
Prison Time: A Class E felony conviction carries a sentence of up to four years in state prison.
Fines and Probation: Courts can also impose steep financial fines, mandatory surcharges, and a period of probation.
Additional Consequences
Immigration Status: Non-citizens face a high risk of deportation or denial of legal status if convicted of a felony.
Future Employment: A felony record makes it very difficult to pass background checks for legal jobs or obtain professional licenses later in life.
Business Closures: Unlicensed locations or parlors risk immediate police raids, asset seizures, and forced shutdown by the city.
Given the number of HE guys out there, I'm surprised so many are willing to take the risk. There are so many flaky customers, all it takes is one bad apple to seriously blow up someone's life. I suppose there isn't a large budget for city/state inspectors, so I imagine there isn't much checking going on. But still, there seems to be plenty of risk.