Yes, estimates are free.
No, you do not to be home when the work is being done. However, unless you are wanting an estimate for the whole roof then someone needs to be home so that you can show us where the repair needs to be done. We may need access to the interior of the house if there is a leak.
It all depends on the size of the repair or the size of the roof and what type of roof we will be working on. A repair can take a couple of hours or as much as a couple of days. A complete re-roof may take as long as 2 to 4 days for a shingle roof, tile roofs take 5 to 10 days.
We use whatever the home owner requests.