I went for 6 months without pay. Be prepared to not only financially but also mentally get through this difficult time. My biggest tip is to start in H1 of each year as big companies hardly hire between Oct - Feb. If you start your training start in Dec-Aug cause otherwise you are facing an additional three months after the training sitting and waiting for offers. It was the most stressful time of my life. FDM does absolute zero to support you so don't count on that. You sit in the academy and wait and that's it. Make sure you are prepared for that. If you get your timing right you will get placed before you even finish your training so that's something to remember too!
About the money..It's not much, FDM takes most of the cut the first two years but tbh its more than I ever made before and you get by as long as your not forced to live in London. And after the two years you will be sorted believe me.