I work in an advertisement agency and our client wants to make a LEGO custom made airplane branded with their branding to be given to their offices. Is there anyone who can make the instructions and what parts should we order and we will build them ourselves?
About your question: I don't think anyone will give you instructions+part list without getting some form of payment and you haven't mentioned anything about that, but what are you willing to pay? (I can't do it, so I'm not asking because I'm interested).
You haven't said anything about the scale of the model they want. For the rest of the answer I'm going to assume a scale that means the model will contain some hundred parts.
To address the final part of your question: Depending on what parts are used in the design you want to go with (and the depth of your pockets - some parts are very expensive) there should be no problems in you ordering the parts and building a number of copies - note that it might take quite a bit of time to actually do that, depending on:
- the size of the model
- the skills of the people doing the building
- the building techniques used
If you can find a local builder who wants to take on the task, it might quickly become cheaper to ask them to build a number of copies.
You haven't said where you are, but if there are any LCP's (LEGO certified professionals) near you (or any of the client's offices), this sounds like a job they would like.
Henrik is spot-on with his suggestions for more details and things to think about here.
But I have a particular suggestions for the who part of your question: talk to BigPlanes from youtube that recently started their 777 project. I don't have any contact information for this youtube user, but you could start by making a comment on one of their posts and see how it goes.
You could also try someone that builds Boeing planes on Rebrickable, but I didn't see anybody trying to do a 777 up there yet. One advantage of Rebrickable is that most of the participants are used to creating instructions for their sets.