Can anyone tell me how much a mobile home estimated worth is?

About 1980's or earlier fleet-wood model single wide with larger master bedroom and garden tub with separate bath/shower. A 2nd 8x8 bedroom with a small bathroom in hall. A small kitchen, dining, bar living room combo. And a very small laundry room in hall. Not in great shape, but somewhat livable if your standards are low. Needs quite of bit of work to repair a leak on roof, floor repair and leaky faucets. The trailer sits on a spot that is not owned by trailer owner. The plumbing pipes need reworked and the septic tank needs reworking. Most of the windows are cracked and don't seal properly. The floors have holes in places. I want to make a fair offer just to get the people out of it so I can either improve or move it out as it is an eyesore.