It seems fair enough.  I've got no problem paying for what I use.  The compensation would have to be realistic relative to the condition of the fence.  How about you?  Iowa fence law says you could get a neighbor to pay for half of the fence to be used for your purposes.  Many have done just that.  If you were running cattle in Iowa, would you be willing to compensate any of your neighbors who put in and maintained a fence on your behalf when the fence was otherwise of no use to them?