You said "like" SAP, not SAP only, so let me suggest Cobol. It's a language we rarely hear about but it is an exotic niche that could also pay well. Well, this is just an idea, I'm not an expert on Cobol.
I don' think so. Most COBOL jobs I've seen want like 10-15 years experience which is effectively impossible to obtain in 2017.
Maybe, but I don't know. A lot of the COBOL-herders for billing systems for utilities are retiring and people are searching for a journeyman coder they can train. For now, the situation is held together by these older people retiring, and then coming back on as consultants until replacements are found and trained -- and they aren't cheap.