Living off 400 leva no problem.
You just adopbt 100% the Bulgarian way of life, work the land for your fruit and veg, keep livestock for your meat and eggs, learn how to preserve everything, doing this you are outside all day and not burning electric or Logs, if you do it right you will be too tired to sit up and watch the standard 3 channel tv or light your fire, you would crawl into bed recharge your batteries ready for next day hard work, if you drink or smoke, then you will be making your own wine/rakia, growing your own tobacco and smoking that. Out that black painted drum on the roof for hot showers in summer
Be warned the moment you start thinking about the how it all used to be you have lost the battle. The Bulgarians can do this all we have to do is change our mind set.