I started my business as a sub, working for a number of landscapers and contractors I had built relationships with through my prior job as a landscape distributor. I was doing fert/pest, irrigation & lighting. I had planned to never be hired directly and only do sub work.
Now we are a landscape construction and do everything except for maintenance (adding that next season). We still do a lot of sub work and sub out a large amount of work ourselves. This season we were subbed for well over 250k and probably subbed out about 200k or so.
The standard with us is that we tack on 10-20% when work is subbed out, and know that contractors do the same to us. So if I get a large construction install and the deck contractor charges me 30k, I tack on an additional 3-6k for myself. But with referrals we do not pay a kickback or expect one in return, we simply refer the customer to the other contractor that we trust to do a good job. The reason to sub rather than refer is that you retain control over the products and design. Often times when the customer has direct contract with other contractors they may decide between them to make changes, these changes can have a negative impact on the overall design. For example we had one a few years ago that was a full back yard landscape install. The customer hired their own contractor to build the deck. We had good communication between us, but then between the two of them they decided to move the location of the deck stairs. This caused us to have to make large changes in the patio design and retaining wall, the changes to the wall were enough that we had to bring in an engineer and delayed the project 4 weeks as we had to go through all of the approval and permitting process again.
With sub contracting, changes can still be made but we must be a part of the project. The deck contractor signs a contract with us, not the homeowner. So if they make the HO's changes without our authorizations they are not building the deck per our contract. This makes sure we are always in the loop and can be sure all changes will still work with our intended design.
As a far as what we sub, the most common is fencing, decks, pools, concrete/asphalt, and large excavation that we can not do with our mini, or land clearing that that would take to long with just a couple of skids and minis
Why do people not respect us as they do other tradesmen? Because every Tom, Dick, and Harry doesn't think he can be a plumber or electrician!