I have simair situation and I have few customers that called me to give the estamate over the phone even with internet on the Email ( this part I have to be carefull ) and tell them I don't useally quote it over the phone or email without photo unless I am at the location then I can able determted what the charge will be.
Of course there will be a service call fee add to it until the main contract is drawen up properly then I can take the SC fee and use that to the contract as cridet.
That how I knock the price shopper out of the list.
Sure I give them the X numbers of days before I start work and also I hold the price for XX of days before it expired ( most case useally 20 days for resdentails the commercals useally either 15 or 30 days but never more that.)
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)