I am confused in choosing what to study next.?

I have done BS in Environmental Planning and Management Sciences and i have a Post-graduate diploma in Disaster Preparedness and Management.in both things i had GIS(geographic information Systems) Common and i am interested in Geography and Computers naturally so i want to do MS in GIS but i am confused that will it be a good choice considering the market value and jobs,as a substitute i am considering Sustainable Development,please suggest what should i go for but the point is that i can make good money.yeah i know its not all about money but lets be realistic money is important.