When I subbed work from someone else (me supplying van, tools, water etc.), I got 60% of the take. Any bad debts/lost customers were the other guy's loss. It felt tight some days but reasonably OK on others - depending on the work type. It did get a bit easier once I knew my way around - that bit is very important because there can be a fair bit of down time while learning the round.
It helped that the other guy tended to price a bit higher than me too, something I learned from when the arrangement eventually ended.
75% would have been more like it but I'm not complaining. It was extra work at a time when I needed it.