I just did my first large commercial display this year for the local park district here. Its is a drive thru display with a short 5 minute show at the end. The one thing I learned this year is there was a lot to learn the first time around and I have been doing my own computerized display for 5 years now. All the other stuff said above about insurance and dont under value your time is right on. Spell every single item you are providing out in the contract down to number of cords and other materials. Than add 10-15% more in your end figure for incidentals. I would let them own everything. Renting it for a month a year I never figured up to be cost effective for the you or the client. Too much up front. Installation: Make sure you have enough time to get it done before start up date and than add at least a few days for weather. Find out what exactly you can and cannot do. If you are putting lights on the building, your client may not want you drilling holes or hammering nails in their shiny walls or other structures. They may not want you running cords over side walks and such. Make sure you know ahead of time so you can design around those restrictions. Dont forget to add time if you are taking part in the tear down of the lights. Are you doing nightly start up of the display to make sure its 100%? Dont forget to add that if you are. I spend an hour each show night to make sure the display is running smoothly. Now to the tone of your post. This sounds like this may be your first year with LOR. If this is the case, I would not touch a commercial display without a year or two experience on your own home. There is a lot you learn from doing your own home display that you can not learn anywhere else. You can get a good feel for installing lights, building display items, how long those things take. Tricks for installation, Tools needed. Going in blind will not turn out good for you or your client. I know your thinking, these are just Christmas lights. Only problem is they are not your lights and its not your money. Your client has certain expectation you need to meet and you need to do your best to exceed them. One major thing I totally under-estimated this first year. The amount of stress that comes along with projects like this and spending other peoples money. I never had this much stress with my home display. Stress from stuff you can not control like vendor issues that were not huge issues before. (quality or supply ability) I needed 8 Show Time controllers for the display and did not get them till like 3 weeks before the opening night. I was almost to the point of talking to the client about other alternatives. I had some LED color issues. I'm sure we all felt some of that stress this year, but when you have a locked in set start up date, its makes you nervous. With my home display, if it does not run on Dec. 2nd and starts DEc. 4th....life goes on. When your client has spent 2k in advertising 6pm, Dec. 2nd. That show better be running at 6pm, Dec. 2nd. In any case, good luck with your display whether it be home or commercial!!!