@Jonathan Trimboli when I first got started it was a combination of getting direct bids or knowing the prices of materials I was using and then just estimating the labor costs from there. I spent a lot of time at HD and Lowe's to learn pricing and this really helped me. I wasn't always accurate, but if you have enough of a cushion in the deal I never found myself in much trouble.
That's a hard one and honestly it is every RE persons "Special Sauce" to their "Big Mac". You may know a Rockstar furnace person who runs cash and you get them in for 65% of retail. You may have a crew you are already paying and can have them do half days between other higher paying gigs and it;s just so worth it to send them out. So your costs will vary. Your landscaping company may do 15 clients in the neighborhood and make those costs almost nil. So as much as I would like to give good advice, your market and contacts will make huge game changing differences.