When is a new roof necessary?

I have a newbie question here, at what point do you stop patching a roof and put a new one on? I’m about to start work on a house where you can see daylight through the roof. My new contractor is telling me he can fix it by bracing and supporting it from the bottom and sealing it from the top, but I’m skeptical.

https://dl.dropboxusercontent.com/u/2467033/2013-11-15%2016.58.32.jpg

https://dl.dropboxusercontent.com/u/2467033/2013-11-15%2016.58.40.jpg

https://dl.dropboxusercontent.com/u/2467033/2013-11-15%2017.03.19.jpg

https://dl.dropboxusercontent.com/u/2467033/2013-11-15%2017.03.32.jpg

https://dl.dropboxusercontent.com/u/2467033/2013-11-14%2016.33.26.jpg

Have someone who knows what they’re doing patch it and move on. The rubber coating compound can mask almost any issue, and putting a new roof on an old trailer is too big an investment for the value of the home. Of course, the other option is to use the hole as a selling tool – a free skylight and a shower that does not flow through their water meter.