How do I calculate cost benefit analysis of treatments with a life of 20 years and interest rates of 16%?

Question

I have 8 treatments to compare. 4 have immediate benefits while 4 will have their benefits spread over 20 years. However all the costs will be incurred in the first year. The current lending rates are about 16% annually.

Answer 1

Prepare a 20 year spreadsheet.

The 'cost' column is easy = start yr. 1 with the initial cost and each year add 16% on top to get the start cost for the next yerar. By the end of year 20 you will have the total cost. (it is the start cost for yr. 21)

The Benefit columns for the 4 'immediate benefit' treatments will have the same value in each year .. the total will be the sum (i.e. 20x the 1st year benefit)

For the other 4 treatments the benefits will differ from year to year. The total is still the sum ..

Notes
If you are borrowing at 16% in order to finance these treatments, your Credit Rating must be crap and the Benefits will need to be really high ...
No adjustments have been made for inflation (which reduces effective Interest rate) not for any increase in the benefits
'Mortality' is ignored (costs are paid up front .. what happens if one of the 'benefit' streams 'dies off early' eg. due to accident ?)