You can make your own: To make buttermilk, use 1 cup milk and 1 tablespoon lemon juice or white vinegar. Allow it to sit for a few minutes. If you do purchase buttermilk and have extra, freeze it in 1 cup containers or in Ziplock bags. You can also purchase powdered buttermilk in grocery stores.
Straight-line depreciation allows an equal portion of the laptop's cost to be claimed in each year over the total depreciation period. If the cost of the computer was $1,000, for example, then $200 a year can be included in the company's total depreciation amount each year for five years.
Website/trade/domain names; Acquired technology and others; So 30-years for Goodwill seems fine, but the other 4 categories, which are probably where the value of that 50K website lie are depreciated differently. I think it comes down to the average lifetime of the intangible asset. I know Demand Media was depreciating their Content over a 5-year period.