How do you fix this

http://www.youtube.com/watch?v=mVoaAgiVErs&feature=youtube_gdata_player. The video shows the soffit problem I seem to just keep running into lately

bid the job to do the proper repair.
Drop gutter, remove fascia, then soffit, intall proper j channel.
instead of using penny nails, small sheet metal screws will keep it together forever.

or like many do, ( I dont) foam it. I have seen some foam jobs that just wants to make you scream and pull your hair out.....

Remove vinyl .......install 2x backer......install C channel,,,,,,,,,,screw vinyl into 2x blocking,,

use 3x5 "roof to wall" at areas under valleys,,,,,,(block as well)

Outsource to a licensed builder. There are plenty looking for work...

Looks like they just used siding as soffit material and set it on top of the J channel on the wall. To fix it right you will have to drop the gutters and face metal, take down and throw away the "soffit". Then install C channel above the existing J channel, cut and install actual soffit material put on new face metal and reinstall the gutters. I would say 30 to 35 dollars a foot for 1 story and 35 to 40 per foot for 2 story. So if its a normal house for here probably 250 ft, 2 guys 10 to 12hrs 8500 bucks thats an ok day if you can sell it. Merely my opinion, and an approx price.

It looks to me like they used solid vinyl soffit but failed to put the F-channel against the house. You CAN remove that soffit without tearing off the gutter and fascia. Just remove the existing soffit panels, Install the proper F-Channel then Slide the soffit panels back in from the end.

That is a bad one and you have got some good asvice on the proper fix. I have a suspician that your customer is not economically able to do the right thing. I would tell them the right thing and tell them an economicaly deprived engineering. I think you could use an industrial adhesive not foam and put a bead down the house side and probably some white screws fairly frequently. Pull the outside in with screws and maybe some glue..
You know how much per hour you want to make multiply it, figure in some time for unexpected things, add your materials.
Adhesives have come a long way. I would bill it as an exclusion not a repair.

F channel thank you! Actually what I meant just didnt come out that way, my appologies.