Without exception, ALL contractors develop "recall lists" of people they know are really good at what they do. 

Some contractors keep entire staffs on recall, because they don't know when to expect a market surge or a stall.  Once the contractor gets a job lead that shows real promise, he begins the rounds on his recall list until he finds everyone he'll need for that job.  He reserves his crew on his word: construction roughnecks put more store by an honest man's word than a yuppie's contract.

Then, once he knows exactly who will be doing what, he files his bid.  Until the contractor KNOWS he has the bid, everyone is on standby: we know we're going to work sometime soon, turn down less lucrative offers.

If the contract goes sideways, the recalled workers know that it how it goes.  If it happens twice, we know better than to respond to his third call. 

Usually, we go to work and stay on the job until we have a final inspection and occupancy. 

The one thing I avoid like the plague is a temporary staffing agency: they pay pennies and they are not called slave markets for nothing.