Cost Worksheet vs. Rate Lock Agreement: What’s the Real Difference for Homebuyers?

When you’re getting a mortgage, you might see both a Cost Worksheet and a Rate Lock Agreement from your lender.

At first glance, they both seem tied to your loan’s pricing — but they serve different purposes at different stages of your homebuying process.

A Cost Worksheet is an early estimate of your loan’s potential costs and cash-to-close. A Rate Lock Agreement is a formal, time-sensitive contract that guarantees your interest rate for a set period.

Understanding how they differ helps you shop smarter, compare lenders accurately, and lock in your loan terms with confidence.

Key Takeaways

Cost Worksheet:

A detailed, lender-generated estimate of projected fees, third-party costs, and total cash-to-close — unofficial, but great for comparison.

Rate Lock Agreement:

A formal, written contract confirming your interest rate and pricing is guaranteed for a specific number of days — typically 30 to 60 days, but lock periods may vary by lender.

Biggest Difference:

Cost Worksheet = estimate.

Rate Lock Agreement = commitment.

💡 Pro Tip: Before locking your rate, upload your Loan Estimate to Fincast, which compares your Loan Estimate against vetted lenders to see if more competitive deals are available, with no extra credit pulls or spam.

What Is a Cost Worksheet?

A Cost Worksheet (sometimes called a “Loan Cost Estimate,” “Itemized Fee Worksheet,” or other lender-specific names) is an early, lender-provided breakdown of your loan’s projected costs.

It’s not standardized or legally required, but it’s often your first detailed look at how much your mortgage might cost — helping you compare lenders before you apply.

A Cost Worksheet typically includes:

• Loan amount, interest rate, and term assumptions

• Estimated monthly payment

• Lender fees (origination, underwriting, processing)

• Third-party fees (appraisal, title, escrow)

• Prepaid items (taxes, insurance, interest)

• Estimated total cash to close

👉 Think of a Cost Worksheet as your early cost preview — helpful for comparing lenders before committing to one.

What Is a Rate Lock Agreement?

A Rate Lock Agreement (sometimes called a “Rate Lock Confirmation”) is a formal, time-limited contract between you and your lender that guarantees your interest rate and loan pricing for a set number of days.

It’s a key milestone in your loan process — protecting you from rate increases while your loan moves through underwriting and toward closing.

A Rate Lock Agreement typically includes:

• Locked interest rate and loan type

• Lock period (e.g., 30, 45, or 60 days)

• Lock expiration date

• Points, credits, or fees tied to pricing

• Terms for lock extensions or modifications

👉 Think of a Rate Lock Agreement as your rate guarantee — your protection from market volatility while your loan is processed.

Cost Worksheet vs Rate Lock Agreement: Side-by-Side

How Should I Use Both When Buying a Home?

Each serves a distinct purpose — one helps you compare, the other helps you commit.

Step 1: Request Cost Worksheets

Before applying, ask multiple lenders for Cost Worksheets to compare estimated fees, rates, and total costs.

Step 2: Choose a Lender and Apply

Once you’ve reviewed your options, submit your application. Your lender will issue your official Loan Estimate within three business days.

Step 3: Upload to Fincast

Upload your Loan Estimate to Fincast. The platform benchmarks your deal against vetted lenders, allowing you to see whether better pricing or lower fees are available.

Step 4: Lock Your Rate

When you’re satisfied with your lender and rate, request a Rate Lock Agreement. Confirm your rate, lock period, and expiration date in writing.

Step 5: Track Your Lock Expiration

Keep an eye on your lock period. If your closing is delayed, you may need an extension, which may incur a small fee.

Why Both Matter

Your Cost Worksheet helps you compare estimated costs before applying.

Your Rate Lock Agreement protects your final rate once you’ve committed.

Together, they help you move from exploration to execution — ensuring clarity, transparency, and control over your loan terms.

Compare Real Offers Effortlessly Using Fincast

Before locking or closing, verify your deal.

Upload your Loan Estimate to Fincast — the platform benchmarks your offer against vetted lenders to reveal whether better rates or lower fees are available.

✅ No multiple applications

✅ No extra credit pulls

✅ No spam

You’ll see exactly how your deal stacks up — before you close.

FAQs

1. Is a Cost Worksheet the same as a Rate Lock Agreement?

No. A Cost Worksheet estimates your potential loan costs; a Rate Lock Agreement guarantees your rate and pricing.

2. When should I lock my rate?

Typically, once your loan application is complete and you’re satisfied with your lender’s terms.

3. Can my rate change after locking?

No — unless your lock expires or your loan details (such as the amount or program) change.

4. Do I pay for a rate lock?

Usually no, but extended or relocks may involve a fee.

5. How does Fincast help?

Fincast benchmarks your locked deal against vetted lenders — confirming your rate and fees are competitive before you close.

Bottom Line

Cost Worksheet = cost preview.

Rate Lock Agreement = rate guarantee.

One helps you compare lenders early; the other secures your pricing once you’re ready to move forward.

With Fincast, you can verify that both your estimates and your locked terms are working in your favor before you close.

Pro Tips (Save These!)

✅ Request Cost Worksheets from at least three lenders.

✅ Don’t lock your rate until your loan application is ready.

✅ Confirm your lock expiration date in writing.

✅ Ask your lender if they offer a float-down option if rates drop.

✅ Upload your Loan Estimate to Fincast to confirm your deal.

Action Checklist

☑️ Request Cost Worksheets from multiple lenders

☑️ Apply for your loan and review your Loan Estimate

☑️ Upload your Loan Estimate to Fincast for instant benchmarking

☑️ Lock your rate and review your Rate Lock Agreement

☑️ Monitor your lock expiration date

👉 Ready to lock with confidence?

Upload your Loan Estimate to Fincast and confirm your pricing — and your deal — are truly your best yet.