What Is Mortgage Rate Lock Float?
When you're pre-approved for an investment property loan, your lender will ask: "Do you want to lock your rate?" This is one of the most consequential decisions in the mortgage process. Locking at 7.0% means you get 7.0% regardless of whether rates rise to 7.5% or drop to 6.5% before closing. Floating means you gamble on market movement.
For most real estate investors, locking is the safer choice — you've already analyzed the deal at the quoted rate, and your cash flow projections depend on it. A 0.50% rate increase on a $250,000 loan adds $83/month to your payment, potentially turning a cash-flowing property into a break-even deal. The risk of floating rarely justifies the potential savings.
However, there are scenarios where floating makes sense: when the Federal Reserve has signaled rate cuts, when economic data suggests rates will decline before your closing date (30-60 days out), or when your lender offers a "float down" option that lets you lock at a lower rate if rates drop. Understanding this decision is critical for investors who may close on multiple properties per year.
A mortgage rate lock guarantees your interest rate for a set period (typically 30-60 days), while floating means you accept whatever rate is available at closing — a decision that can save or cost thousands depending on market direction.
At a Glance
- What it is: The choice between locking in today's mortgage rate or waiting for a potentially better rate at closing
- Why it matters: A 0.25-0.50% rate difference changes cash flow by $40-$85/month per $250,000 borrowed
- Key metric: Lock period (30-60 days standard), float-down threshold (if available)
- PRIME phase: Invest
How It Works
Rate locks work on a fixed timeline. A standard lock is 30-45 days — the expected time between application and closing. Longer locks (60-90 days) are available but cost more, typically 0.125-0.25% in rate premium. If your closing is delayed beyond the lock period, extending costs an additional 0.125-0.25%.
Floating is pure market speculation. Mortgage rates move daily based on bond market activity, Federal Reserve signals, inflation data, and global economic events. Rates can move 0.125-0.25% in a single day after unexpected economic reports. Floating exposes you to this volatility — potentially beneficial if rates drop, devastating if they spike.
The "float down" option is the best of both worlds. Some lenders offer a float-down provision: you lock your rate, but if rates drop by a defined amount (usually 0.25% or more) before closing, you can renegotiate to the lower rate. This typically costs 0.125% upfront but protects you from rate increases while allowing you to benefit from decreases.
Decision framework for investors. Lock when: your deal analysis requires the current rate for positive cash flow, rates have been trending upward, or you're risk-averse. Float when: the Federal Reserve has explicitly signaled cuts, economic data consistently shows deflationary trends, or your closing is 45+ days away and rates have room to fall. When in doubt, lock — the cost of being wrong on a float (higher rate, worse cash flow) exceeds the benefit of being right (slightly lower rate).
Real-World Example
Jordan in Charlotte, NC. Jordan was under contract on a $280,000 fourplex with a 30-day closing. His lender quoted 7.125% and offered to lock for 30 days. Jordan had been reading that the Fed was likely to cut rates at their meeting in 3 weeks, so he chose to float. Over the next 10 days, rates actually rose 0.25% after a hot inflation report — his rate was now 7.375%. The Fed meeting came and they held rates steady. Jordan closed at 7.375%, paying $50/month more than if he'd locked ($600/year, $18,000 over 30 years). His cash flow dropped from $380/month to $330/month. On his next property, Jordan locked immediately at the quoted rate and never floated again.
Pros & Cons
- Rate lock provides certainty for deal analysis and cash flow projections
- Protects against rate spikes that can destroy deal economics
- Float-down options offer downside protection with upside potential
- Locking removes one variable from an already complex transaction
- Experienced investors can save by strategically floating in clearly declining rate environments
- Locking too early in a declining rate environment costs money versus floating
- Lock extensions are expensive if closing is delayed (0.125-0.25% per extension)
- Short lock periods (15-21 days) offer better rates but create closing pressure
- Float-down options cost extra and aren't available from all lenders
Watch Out
- Lock period must cover your closing timeline. If your closing is 45 days out, a 30-day lock will expire and require an expensive extension. Match the lock period to your realistic closing date plus a 7-10 day buffer.
- Don't chase rate movements. The temptation to float after locking (if rates drop) or panic-lock after floating (if rates rise) leads to costly mistakes. Make the lock/float decision once based on your analysis, and stick with it.
- Verbal locks aren't locks. Get your rate lock in writing from the lender, including the rate, lock period, expiration date, and any float-down provisions. A verbal promise is worthless if rates spike.
The Takeaway
For most real estate investors, locking your mortgage rate immediately upon receiving an acceptable quote is the right move. Your deal analysis depends on a specific rate, and the downside of floating (higher rate, reduced cash flow) usually outweighs the upside (slightly lower rate). If you want flexibility, pay for a float-down option. Save your risk-taking for deal selection, not interest rate speculation.