Hi guys need advice.

I've been selected for a posting and am waiting for G50 clearance. However, I'm aware that there's a chance clearance may fail. Hence, instead of waiting for about 1-2 more months without knowing whether i will fail or pass and get the offer, is it okay for me to take a job offer elsewhere first then quit if mindef offer me? Would it cause any complication to my mindef hiring process if i do this? i also need income so cannot wait indefinitely...