Ok, well I am not sure how detailed you are talking. There needs to be a summary type part and then there can be the nitty gritty details including math and all that for people who understand it; just having the raw technical details is a no go.
Regarding results, thats the problem, you should have some idea of them. It doesnt need to be down to the mW amounts or anything but a rough estimate is good enough with the promise of more concrete values at a later point. It isnt that hard to calculate incoming energy based on time of year and when cloudy and all that kind of stuff. That would be all thats needed to show an estimate.
Regarding cost, once again, this shouldnt have been too hard to calculate to give an estimate. Yes materials pricing will fluxuate some, but typically not in large swings. You take the average roof area in the US, figure out the minimum and maximum amount of materials you would want to use to cover it and then that would give you a base cost; likely good for a couple years assuming no suprises.
In the case of actual examples and photos. That guy didnt sound professional. He should have been able to quote you a cost for doing what he did before he did it; and that cost wouldnt have changed much because he would only have been doing a simple job; suprises would have been unlikely here.
Investors, I would have suggested a contract of some sort there. They should know exactly(or close anyway) what they are getting into before they do it as well as they should know what they have a say in and what they dont. Yes, finding funding can be hard, but having someone use their funding input as a bargaining chip can cause more trouble than its worth. The bargaining should be done before funding starts, not after.
I am going to touch on the pictures topic. I think you lacked some vision on that point. Yea, there may have been junk laying around, but was there a problem with simply moving what you wanted to take the picture of? I mean, it could have been moved outside with a wall for the background. I can understand if there may have been junk laying everywhere and maybe you were also crowded in a city so there wasnt room. In this case, I would have suggested to simply cover the junk with some plain sheets, or set up sheets like a back drop. It would not have mattered if some stuff was dirty, labeling things as under construction etc would have been enough; most people arnt going to be expecting should ultra-clean shiny device.