nowadays 80% of jobs looked at don't even get back to contractors.
so really if you have decided on 1 contractor yet, you can take all the time you want.
if you have decided it would be best to let them know you are nearing a decision and that they are in the ballpark so to speak, just so you have no problems with scheduling.
alot of people forget that a contractor is not siting at home waiting on the phone to ring for their specific project.
we do this for a living, so time is everything.
payments are usually in 1/3.
the way we do it is as follows.
1/3 at beginning
1/3 after rough inspections ( electrical,plumbing, rough framing)
1/3 upon sign off of permit.
depending on size of project a contractor will also ask for a payment for materials along with 1st payment.
everything should be stated on contract.
usually there is no fee for the clerical side of for the smaller to mid size contractors as they do all the clerical work also.