Two programs, ten years, one answer
Loan program comparison and net worth model
Most comparisons stop at the monthly payment. This one takes any two loan programs — 15 against 30 years, fixed against adjustable, two lenders, a refinance or a purchase — and carries both all the way through your finances: amortization, California and federal tax, what your household actually has left over each year, the emergency fund, retirement and taxable accounts, and where your net worth lands at the end of the hold period.
The two programs
Take these from the Loan Estimate. Discount points must be split out separately, because they are deducted over the loan term rather than in the first year.
HELOC and emergency liquidity
A cheaper loan that leaves you short of cash is not automatically the better deal. This is where the model can overrule the winner on cost.
The full model, with your numbers in it
The summary above is the short answer. The workbook is the long one: every assumption, both amortization schedules month by month, the investment-return sweep, and the liquidity and home-price stress tests. Values only, so nothing recalculates and nothing breaks when you edit a cell.
Tax is modelled at California and federal rates
State tax changes the answer, sometimes enough to flip which program wins. This online version only models California. If you live or file anywhere else, ask for the model and tell me your state — I will run it on your own rates.