94 Montero won't start / blown fuse

Hello, I'm new to the community. Just bought a 94 Montero from an individual and it ran for about 2 weeks then stopped working one day. So, i took it into a mechanic and $600.00 later....i'm having the same problem 2 weeks later. Mechanic told me the fuse was blown, and I should just replace it if it happens again. We'll...easier said then done, because it ate up 4 more fuse's without starting. It's the green one under the hood..and idea what could be causing this? Thanks..avoiding the shop ..and another bill

what is the fuse for ????????????

This is probably the starter fuse. Fuses usually blow (always) because of excess current flow, so you most likely have a shorted starter motor or the + starter lead is shorted to the chassis (-).