I would ask the homeowner to get an estimate in writing, since they own the home. This way they have real numbers in hand to explain to folks what they are up against. And take that low bid and add 5k. That will be closer to what you will end up paying.
The next buyer is going to have the same questions as it needs to be disclosed, if it is tested and found to have asbestose. If it is never tested, then no one knows for sure what it contains and does not have to be disclosed. You would need to insist that it is tested during a home inspection, this way you know what you have. It will also help you to make a decision and have real world ##s.