If you are active in the field and continue to upgrade your knowledge and skills, you should be able to pass the RID skills certification within three to five years. Salaries will vary depending on many factors. They do not get employee benefits. Other interpreters work for an agency, business, government organization or school system. You may want to call interpreter referral agencies and school systems to get specific information about the area of interpreting that interests you.
Sign language is no more universal than spoken languages.
England uses British sign Language and Australia uses Australian Sign Language. While it borrows elements from spoken English and old French sign language, it has unique grammatical, lexical and linguistic features of its own. It is not English on the hands. Because ASL is not English, educators have developed a number of signed codes which use ASL vocabulary items, modify them to match English vocabulary, and put them together according to English grammatical rules. Language fluency, be it spoken or visual, requires time, study, immersion in the language community, and constant practice.