To cream off the loot which they could intercept.
They came to find gold or sell products.
Those who were most targetted were passengers and drivers of the carriages which carried gold from the goldfields.
The high numbers of bushrangers in the 1700s and early 1800s were due to the numbers of escaped convicts. Becoming a bushranger was often the only way for an escaped convict to survive. Numbers of bushrangers after 1851 increased as a result of the gold rushes. Coaches or people on horseback carrying gold from the goldfields were easy targets for bushrangers.
Bushrangers caused fear amongst the people of the goldfields, and those who had to convey the gold to the cities. They were particularly known for ambushing coaches with wealthy passengers. Essentially, they made travelling unsafe.
Bushrangers survived by various means. Some of them stole provisions owned by the settlers in outlying areas, helping themselves freely to salted meats, potatoes, onions, flour and so on. They also stole from store owners in the towns. Others hunted wild rabbits and native animals.
Edward Hammond Hargraves
Food that the diggers did not shoot for themselves (such as rabbits and kangaroos) came from the bigger cities. This is why it was so expensive. The small shop owners on the goldfields were in a position to buy in bulk and then charge extreme prices for their goods.
Possibly...A hut like the gold fields or in a tent or maybe they moved around. My best guess is something like what they had on the goldfields (tents and bark huts)
Yes they came
Letters came into the goldfields with other supplies - usually on drays or sulkies being pulled by horses.
People came to the goldfields in Ballarat for the same reason they went to any goldfields, which was in the hope of finding their fortune in gold. The Ballarat goldfields were among the richest in Australia at the time.
Initially, there were no facilities for education on the goldfields. This only came later, after small towns had sprung up around the diggings.