Buying a Second Home With RSU Income: The Lender's View

A senior IC earns $420K ($180K base + $240K RSU) and already has a $1.8M primary-residence mortgage. They want to buy a $1.2M vacation home in Tahoe. The second home mortgage is $960K at 20% down.

Second-home underwriting differs from primary-residence in several ways: higher down payment requirements, stricter DTI thresholds, careful scrutiny of why it’s a “second home” versus an investment property, and harder questions about the stability of the RSU income stream supporting both mortgages.

Primary vs second vs investment

Lenders (and Fannie/Freddie) distinguish three property classifications, each with different rules:

Primary residence. Borrower lives here most of the year. Best rates, lowest down payment.

Second home. Borrower lives here part of the year. Not rented out regularly. Typically 10-15% down minimum for conforming, 20-30% for jumbo. Rate premium of 25-50 bps over primary.

Investment property. Borrower doesn’t live there; it’s rented. 20-25% down minimum. Rate premium of 75-150 bps.

Second-home status requires the property to be:

• Occupied by the borrower some portion of the year
• At least 50 miles from primary (rule of thumb, though not always enforced)
• Not subject to rental agreements or property-management contracts for full-time rental

Borrowers who buy a “second home” but then rent it on Airbnb year-round risk loan fraud allegations. Part-time rental (under 14 days per year, which keeps it tax-free under IRC §280A) is usually fine. Frequent short-term rental is investment-property territory.

Down payment standards

Second-home down payment:

• Conforming second home: 10% minimum (but often 15% practical floor due to pricing)
• Jumbo second home: typically 20-30%

For the $1.2M Tahoe example, that’s $240K-$360K cash down. The borrower with existing $1.8M primary mortgage needs substantial liquid reserves.

DTI stacking

DTI calculation stacks both mortgages:

• Primary mortgage PITI: $14,000/month (on $1.8M loan at current rates)
• Second-home mortgage PITI: $7,800/month (on $960K loan)
• Other debt service: $800/month (car, student loan)
• Total monthly debt: $22,600
• Required income at 43% DTI: $52,500/month, or $630K/year

Our senior IC at $420K/year doesn’t qualify on income alone. They need either:

• Lower loan amounts (bigger down, smaller second mortgage)
• Higher qualifying income (more RSU history, bonus)
• Asset-depletion or private-bank flexibility

Portfolio and private-bank lenders sometimes accept DTI up to 48-50% for strong borrowers.

RSU income double-counting

The underwriter already credited RSU income for the primary mortgage. For the second home, they take another look. Same 2-year rule applies, and if RSU income has declined, it’s trimmed.

For borrowers with growing RSU income, new promotion, larger recent grant, the second-home application might qualify on higher RSU than the primary mortgage used. For declining RSU, it’s lower.

Reserve requirements multiply

Reserves are required on both properties:

• Primary reserve: 6 months primary PITI
• Second-home reserve: 6-12 months second-home PITI
• Both are required post-closing

Total reserves for our example: $14K × 6 + $7.8K × 6 = $130,800 in reserves after closing, in addition to down payment and closing costs.

Appraisal and property considerations

Vacation markets often have specific appraisal challenges:

• Seasonal properties may appraise lower in off-season
• Remote properties have fewer comps
• Coastal and mountain markets have unique flood/fire insurance requirements

Second-home appraisals sometimes require additional inspections (environmental, structural) that don’t apply to primary-residence purchases.

Insurance costs on second homes in high-risk areas (California wildfire, Florida hurricane, coastal erosion) have climbed significantly. Budget 2-3x higher insurance on a Tahoe or coastal second home versus a primary in a low-risk market.

Tax treatment

Mortgage interest on a second home is deductible under IRC §163(h) up to the combined $750K acquisition indebtedness cap (for debt incurred after 12/15/2017). This is a combined cap across primary and second, not separate $750K limits.

Example: Primary mortgage $1.4M (post-TCJA) + second-home mortgage $960K = $2.36M total. Only the first $750K is deductible as qualified residence interest. The remaining $1.61M of interest is not deductible as home mortgage interest.

Property taxes are subject to the $10,000 SALT cap across all property taxes and state income taxes combined.

Using a second home as short-term rental

Many second-home buyers plan to offset costs with occasional Airbnb rental. Tax rules distinguish:

• Under 14 days rental: income excluded from gross income under §280A
• 15+ days rental AND personal use >14 days: mixed-use rental, expenses prorated
• 15+ days rental AND personal use <14 days: rental property, fully taxable

Mortgage implications: if you disclose the plan to rent as “second home” loan, and then rent >50 days per year or use property-management service, you may have misrepresented the property type. Safer approach: originate as investment property if substantial rental is planned.

Private bank flexibility

Wealth-desk lenders (Schwab, Morgan Stanley, JPM Private Bank, UBS) often treat second-home purchases more flexibly:

• Combined-property DTI treatment (net income after primary PITI)
• Asset-depletion augmentation for investable-asset-rich borrowers
• Pledged-asset structures for down payment
• Portfolio approach where both mortgages are held in-house

For borrowers with $1M+ investment relationship, these programs unlock second-home purchases that wouldn’t qualify at standard jumbo.

Frequently asked

How does a second home affect my primary-residence mortgage? It doesn’t change the primary mortgage. The second-home PITI just adds to your DTI for future underwriting decisions (refinance, HELOC, etc.).

Can I use RSU income vested in the last 12 months? Same 2-year rule. Recent RSU grants need 2 years of vesting history. If RSU growth accelerated recently, the averaged figure may under-represent current income.

Does trailing-nexus affect second-home purchase? Only indirectly. If you move from California to Nevada but still owe California on trailing-nexus RSU income, your effective after-tax cash flow is lower. Lenders don’t specifically track this, but it affects your actual ability to service both mortgages.

What about §6501 statute and dual-property tax records? The 3-year assessment period applies to the tax return treatment of both properties. Keep property tax records, mortgage interest statements (1098s), and rental income (if any) for 7 years.

Does IRMAA care about mortgage payments? No. Mortgage payments don’t flow through to MAGI. But if you sell stock to fund the second home down payment, the capital gains do affect MAGI and IRMAA two years out.