Squizzy hit the nail on the head, demo is mostly about trucking and disposal.
Getting the structure down is the easy and fun part, hauling all the debris out profitably is the tricky part. I mainly do small structures like houses, sheds, etc so the advice below pertains to that type of structure. Safety is also paramount in any demo project and changes due to the type, location and materials involved. Definetely check into your local/state asbestos and demolition rules prior to pricing any job. The asbestos that we run into on residential demo is usually in the old siding ( I don't do abatement). In AL any commercial structure has to have an inspection and clean air permit from the state Environmental Department, it is not required on residential but the asbestos rules still apply.
First question - How does your local landfill(s) or hauling company(s) charge for disposal, by the ton or CY? That is very important, if they charge by the CY then it makes your estimating easier. If they charge by the ton then you have many more variables. What is the price per ton/CY for disposal and what do the hauling companies charge for a 30CY can in your area? Do the hauling companies charge a flat rate per box or haul+rental+tonnage? If you are going to use hauling companies you can negotiate a better rate for demo since the box will turn quickly - IE drop the box, load it out in 15-20 mins and it's gone. In the roll-off business you want your boxes turning quickly as opposed to sitting on a job for a month. The box only makes money when it is either being dumped or being delivered.
In my area all the landfills charge by the ton. We have 10 or so but only haul regularly to 4. The reason why I say paying by the ton has more variables is this:
I bid a burned out 900SF house to demo. The windows were boarded up and I could only see the living room through an opening - I was too lazy to take down the plywood and go inside, which turned out to be a big mistake. The rear bedroom and kitchen was not damaged by the fire and was filled with personal items to boot. Once I started in tearing down the house I found alot of wet clothes, books, kitchen items etc. This increased my tonnage and of course I bid the job hard. I ended up with more volume and tonnage due to the wet contents.
If you are paying by the ton or CY you will want to seperate as much concrete, brick, asphalt and other "inert" materials to be disposed of seperately. Around these parts these types of items are not regulated waste and can be used as beneficial fill. I have a place we haul this type material to and of course no tip fee.
Will you be hauling the debris yourself or contract out? I am a partner in a roll-off company and also have 1 dumptruck. When I do demo I plan which route and landfill to go to and incorporate that into my estimate (Google Earth works very well for this). I pay my roll-off company a set hauling fee and I pay the tip bill directly. I am able to save some money, the roll-off company makes money but the responsibiliy to acurrately estimate the tonnage is still on me.
Having control of the roll-off's coming in and out makes a big difference on the performance and bottom line of the project. I have the luxury of pulling an extra truck in whenever I need it to keep the job going smoothly during the load out stage. This is important since a profitable demo job is about speed and efficiency - get in and get out.
The Holy Grail of demo is how to estimate it. I use historical costs to estimate a SF cost plus the variables of contents inside, condition of structure (partially burned, intact, etc), hauling distance, amount of inert materials, access to the site and the time I think it will take to complete the job.
Then you have the different materials you will be working with that will either break/crunch up easily or not so easily. 3/4" plywood subfoor is a pain and will take up volume in a can/truck. OSB will break up easier and if it is an old structure with 2x decking/subflooring then you can get a tighter packed can. Then you just have the variables of "hidden" items. Like the front porch that had wood flooring but turned out to have reinforced 6" concrete underneath it.:Banghead
With demo you will win some and loose some. With experience and historical job cost numbers you will be able to get closer on every job.
..but the big demo mobs have their private tipping arrangements and I found it too hard to compete.