If you really don't want to walk away (which I get, the community might be relatively large and have useful content there), then arrange a proper discussion with the owner about being given some limited admin permissions. Reassure him that you're fine with him limiting those permissions to not allow you to do anything harmful, but tell him that it's clear he doesn't have the time to dedicate to the forum and you'd really appreciate the opportunity of helping out and clearing the place up. If you've already been doing a good job of keeping things ticking over with the limited moderator permissions you already have, he might just be willing to offer that extra bit of trust.
Ultimately, I do feel that what Al specifically mentioned should be your realistic option - if the current owner wants a six-figure price tag, I'm guessing the community is either huge, or is in a niche that has huge potential for advertising and associated income - if you have the time on your hands to take on such a site, then you almost definitely have the time on your hands to have a real crack at doing your own forum in the same niche, and attempting to migrate over the members that are also disillusioned with the inattention paid to the current forum... you'll find plenty of resources, advice and support here at Administrata too to help you along the journey.
Ultimately, I do feel that what Al specifically mentioned should be your realistic option - if the current owner wants a six-figure price tag, I'm guessing the community is either huge, or is in a niche that has huge potential for advertising and associated income - if you have the time on your hands to take on such a site, then you almost definitely have the time on your hands to have a real crack at doing your own forum in the same niche, and attempting to migrate over the members that are also disillusioned with the inattention paid to the current forum... you'll find plenty of resources, advice and support here at Administrata too to help you along the journey.
