Generally in the US, at least in my experience, a 'professional' occupation usually means doctor, lawyer, or dentist. I see you are a software engineer. Even during the big boom in the late 90's, when Congress passed a law providing for additional visas for IT people, they had to have a job and a sponsor to get into the US. The pattern usually was to come over with a job and a specific length contract, find another job with a company that would assume your visa and sponsor you for a green card, and then once you had the green card, you could set up as a consultant.
However, the extra visas are gone, and it's a lot harder to find work in IT. Have you checked some of the big job sites? That would give you some idea of the need for your particular specialty.