In general the qualifications to teach English are a degree and a TEFL certificate. Often it really doesn't matter what degree you have but obviously it helps (in both finding work and teaching) if your degree is related to English.
You could go for a straightforward English degree or you could go for a more specialised TEFL degree. Personally I would advise against the latter as it's very job specific and if you decide later not to go into teaching English you are stuck with a degree which only really applies to that profession.
As for the TEFL certificate almost any will do for a first job so either in-house or online is fine.
As for finding work, yes it is fairly easy to find a job and the signs are that it is going to continue that way. There are so many places where you can teach that it very much depends on your preference. Where do you want to go?
North Americans often opt for Asia - China, Japan, Korea, Thailand, Vietnam - or South America. Europe is out because of visa issues.
This article is a useful Introduction to TEFL