I am not sure, why you took 100 as a figure. I guess it may be notional and arbitary taken as it is always good thet resource should decide what numbers you should keep ideally. The covered space requireemnt for 100 gaots will be 1500 Sqft and double of it as open space/paddock for free movement of goats. This excludes space for kids , which may be taken under consideration. However it is suggested that kids should must have separate house or a partition will with doe house. 4 to 5 acre of fodder land cultivated insensively can meet the fodder requirement for your goats. The cost of Black bengal goat (Native breed in Bihar, bengal) is around Rs 2000 per goat. Working capital for 100 gaots will be around 1 lakh Rs. Considering housing cost of Rs one lak (excluding land cost), the total required investment will be in tune of Rs 5 lakh.
Unfortunately, Government goat farm at Purnea in bihar is almost defunct and can not provide apprpropriate training. you may contact thegoattrust at gmail.com for training in this region. Governemnt can provide you loan under PMRY, SGSY and some other schemes. One thing is sure, if you demonstrate success, local adminitration will support you through their extension program funds and will link you with different promotional schemes. However this all will come if you prove your success and is commercially demnstrable and succesful. Intial support from government will come with a lot of bureaucratic hassles and will hardly ensure your success in the business. Start small and beautiful with your effort and success will attract others to come to support you.