Since you don't own the house, you MUST get yourself an ASHI-Approved Home Inspection!!! Tuit-suite (sp). For about $300, you can have the Inspector give you a good estimate of what it would cost to 'replace' / 'repair' / 'add' something to the house. This is one of the capabilities of the Inspector! It's their job. NOT just any Home Inspector. (I'm not one, nor do I work for one, or advertise for one. It's just the thing to have done.) I didn't know you were 'interested' in buying the house. OTherwise, I would have answer differently the first time.
When you're looking to spend 100's of 1000's of $$$ over 15 - 30 years, $300 is nothing. It's $$$ well spent. Also, get yourself a decent Real Estate Attorney too. Their fee can range from $250 - $1000. Talk to people who have bought homes recently. Oh, I suggest you don't use a Home Inspector that's recommended by the Realtor. There's a very high potential for conflict-of-interest. Go ASHI and talk to friends.