The quote of $120,000 is certainly hefty, and perhaps he did spend so much to do it up just that way----the way he wanted it. I see quite often the examples of folks being creative at their homes, and doing certain things and investing their money in a way which satisfies them, then, and while they live there. I guess folks call that value-in-use. Does the quote of $120K mean that one should assign $120K of market value to the basement ? While I rarely ask for someone to show me records of invoices paid for special contractors, or materials purchased (for the do-it-your-selfer guy) I must wonder about these bold and fast quotes of what someone "spent" to do something. This past summer I had one order where I was greeted at the front door by a guy who IMMEDIATELY said, "You the appraiser ? You know, I spent $50K on landscaping this place." .....and proceeded to point his finger out and sweep his arm through the air from left to right. I simply said , "it does look nice, I am sure you have those receipts from that work to show me". This was a place looking to re-fi and the aggressive "estimate" on the order was a focus toward what would be 58% value increase over what he paid 18 months earlier. Yes, it was c.o.d., and his wife gave me the check before I left. By time I was back at office there was call to me from his fast-Eddie loan broker in CA saying that the "h/o was complaining that I was being pushy about asking him questions about his house". ......and boy, are they in a rush, so, when will the report be written up?.....to which I said, what report ?, if your client is going to gripe about someone asking for information about his property, then I guess someone else is going to be doing this report, not me. Uh...Uh....Uh.....Uh, (click), ...and the check was promptly mailed back. Sorry, to inject my story there, but sometimes.... Your task may require some extra time and fee, and finding comp sales with unique basement details , that have SOLD, will be important. Take lots of interior photos. If this place has never been listed, never had a legitimate offer to purchase placed on it, then it certainly is a challenging assignment.