@andys1027
Interest doesn't count for cost basis. That the cost of borrowing the money, not the cost of the property itself.
The HOA fee doesn't help, it's not deductible or a cost adjustment.
However (and this brings up an important point about condos), some parts of the HOA fee might adjust your basis, if you paid special assessments for property improvements (not repairs or maintenance). Suppose that in 2000, the condo association decided to completely renovate the common areas, and your share was $100 per month for 10 years. If that work met the definition of an improvement (as discussed in publication 523), then the cost of the improvement adds to your cost basis ($12,000 in my example). But only the cost of special assessments for improvements. Costs for repairs, regular maintenance, taxes, and so on do not adjust your cost basis. If you don't remember the details of special assessments for improvements, the HOA might have records that can help you.
The fact that the rebuilt condo is significantly improved would help you if you had paid for it out of your own pocket, but because it was paid for by insurance, it doesn't help you in the same way. The insurance payment cancels out the lost value from the fire, leaving you with the same basis you had before the fire.
Your tax return will include a form 8489 and schedule D, they will automatically be prepared when you indicate you sold your home. Go to the section for "sales of stocks and other property" and choose "your home" from the list. You will be asked about the cost, selling price, the dates you bought, sold, and lived in the home, and may a couple other important questions. You don't need to send any other proof with your tax return, but keep documents related to the purchase, sale and fire for at least 3 years in case of audit.
