As others have stated, asbestos was incorporated into many different materials and can have many different appearances.
One of the many uses of asbestos was heating system pipe insulation. It may have been used for other types of pipes as well. Typically on a heating pipe asbestos insulation is in the form of a corrugated sheet wrapped around the pipe and taped. If you can actually see it from the end, it looks like cardboard, on the pipe just like paper wrapped around the pipe. There were other forms, so just because it does not look like that does not mean it is not asbestos.
If you are seriously considering purchasing this house, you really should order a home inspection. Do not trust what your realtor has to say, although he or she is working for you some tend to think they know more than they really do. Certainly don't trust the seller's realtor, they are trying to sell a house. Also, I would not accept an inspection report prepared on behalf of the seller or seller's agent at face value.
You should have the inspection to identify issues other than this as well. A quality inspection may save you money on the purchase price and will certainly give you a better idea what to expect in the way of maintenance and repairs. I understand dad is a carpenter, but being a carpenter and a qualified inspector are very different fields. He would certainly be helpful in fixing problems but may not know all of the places to look.
If your inspector also suspects asbestos, a test should be ordered for an additional cost. The seller should cover at least part of this cost.
If it is asbestos, I would still not rule out purchasing the house if everything else suits you. If the system is in use, it may be OK to encapsulate the material and save the cost of removal. If removal is required, you can do it yourself once you are the homeowner in most locations. This type of material is fairly easy to deal with given a bit of reading and taking the proper precautions. Do not just jump in and start tearing it out without understanding the proper procedure, as you will contaminate other parts of the house. At some point in the future, I expect that testing will be required for all houses built before the substance was removed from production in which case an improper removal may cause problems when you sell.