From my recent experience as skaven clan Eshin, at turn 90 I had about 300000 cash & -30000 income per turn. After keeping expending for 10 turns, at turn 102 i found i had 500000 cash & -10000 per turn. it should be post-battle looting that gave me so much money.
And during this 10 turn i built many building that also cost a lot, which meant i got way more than 200000 from looting.
it's not quite common since not all races can have so high looting income like skaven. However if we can know how many we got, i believe we can handle our finance way more effectively