Most people assume a reverse mortgage line of credit works like a HELOC: you get approved for a set amount, and that number stays put until the lender decides otherwise. A Home Equity Conversion Mortgage (HECM) line of credit does something no other credit line in America does. The amount available to you increases every year, automatically, as long as any portion of it sits unused.
This is not a promotional gimmick. It is a structural feature written into HUD’s program rules. And over a 15-year retirement, it changes the strategy entirely.
How the growth actually works
Each month, the unused portion of a HECM line of credit grows at a rate equal to the loan’s note rate plus the annual mortgage insurance premium (currently 0.5%), compounded monthly. If the note rate is 7.0%, the line grows at roughly 7.5% a year. If the note rate is 6.0%, it grows at roughly 6.5%. The growth is contractual. It shows up in your loan statements, on the same amortization schedule that shows the balance of anything you have drawn.
The part that surprises even financial advisors
Here is the detail most people miss: the growth applies to your original principal limit as calculated at closing, not to your home’s current market value, and not just to the portion you have not spent.
So a line of credit established at $500,000 keeps compounding on that contractual schedule even during a real estate downturn, because the principal limit was fixed at closing. The non-recourse protections I wrote about earlier this week are what make this work: you or your heirs will never owe more than the home is worth, no matter how much the line has grown.
What 15 years of patience looks like
Suppose a 62-year-old opens a HECM line of credit with a $500,000 principal limit and never draws a dollar. Assuming a 7.5% growth rate, compounded monthly:
| Years since opening | Your age | Available credit |
|---|---|---|
| 0 | 62 | $500,000 |
| 3 | 65 | $625,723 |
| 5 | 67 | $726,647 |
| 7 | 69 | $843,850 |
| 10 | 72 | $1,056,032 |
| 12 | 74 | $1,226,362 |
| 15 | 77 | $1,534,726 |
This is a hypothetical illustration. It assumes a constant 7.5% growth rate compounded monthly, which no one can promise. Actual rates vary with the note rate in effect at the time. The point is the mechanic, not the exact number.
A line that started at $500,000 has tripled without a single draw. That is what makes this feature a strategic asset rather than just a borrowing tool.
Why a HELOC cannot do this
A traditional home equity line of credit is a fine product with three structural weaknesses in a long retirement:
- The limit is fixed. $500,000 approved is $500,000 forever, regardless of inflation or how long you live.
- The lender can freeze or reduce it. In 2008 and 2009, banks slashed HELOC access across the board, often for the very borrowers who needed it most. It happens exactly when markets fall.
- It requires payments. A HELOC adds a monthly obligation to a retirement budget.
A HECM line of credit inverts each of these. It grows on a contractual schedule, it cannot be frozen or reduced as long as you meet your borrower obligations (paying property taxes and insurance, maintaining the home, keeping it as your primary residence), and it requires no monthly mortgage payment. And it is non-recourse: repayment is capped at the home’s value.
Three ways to use a growing credit line strategically
1. A standby reserve against sequence-of-returns risk. The danger in retirement is not the average return, it is the order of returns. A drawdown in the first years of retirement does damage that later gains never fully repair. A growing standby line means bad markets become the years you tap housing wealth instead of selling stocks at the bottom. I covered a real version of this in this week’s case study.
2. Funding Roth conversions. Converting a traditional IRA to a Roth is one of the highest-value moves a retiree with a paid-off home can make, but the tax bill lands in the years you can least afford the cash outflow. A growing line of credit can cover the conversion taxes from housing wealth, letting the portfolio stay invested. This is a topic I will go deep on in a future post.
3. Open early, use later. Opening at 62 means accepting a lower principal limit than you would get at 70. But it also means a growth runway that is eight years longer. Because the compounding is on the entire undrawn limit, in many modeled scenarios the early-opened line overtakes the wait-and-open line well before age 80. The right answer depends on your rates, your home value, and your plan, which is exactly why modeling it matters.
But what about the costs?
HECMs are not free. There is an up-front mortgage insurance premium, closing costs, and ongoing mortgage insurance. Anyone who tells you otherwise is not being straight with you.
What the cost objection misses is the base the growth compounds on. The up-front costs are a fraction of the principal limit, and the growth applies to the entire undrawn amount, every month, for as long as the line sits unused. Over 10 or more years, the compounding has historically dwarfed the costs. The feature was designed by HUD to keep the line’s purchasing power in step with inflation and home values. It is insurance against outliving your borrowing power, priced like a loan you did not take.
What I tell skeptical clients
In years of originating these loans, the growth feature is the first thing that makes skeptics lean in and the last thing they believe. It sounds too good to be true, so I show them instead of telling them: the growth rate is printed in the loan agreement, the growth appears on every periodic statement, and HUD’s own program documentation describes it. HUD’s HECM page is a good place to verify what I am describing before you talk to anyone, including me.
See the growth in your own numbers
Reading about compounding is one thing. Watching your own line grow in a 30-year projection is another. The Perpetual Retirement calculator models a standby line of credit alongside your portfolio, Social Security, and any Bitcoin holdings, so you can see exactly what a growing reserve does to your plan’s longevity.
Tane Cabe, NMLS 78590, Barrett Financial Corp, NMLS 181106. This article is a hypothetical illustration for educational purposes only and is not a commitment to lend, tax advice, or investment advice. Growth rates vary with market rates; figures shown assume a constant 7.5% annual rate compounded monthly for illustration only. Consult a qualified professional about your situation.
