How to Underwrite a Property in Under 30 Minutes

Question

Hey BP community,

Over the last few years, I’ve looked at hundreds of rental deals — and if there’s one skill that’s moved the needle the most, it’s underwriting deals quickly and confidently. Speed matters in competitive markets, but so does accuracy.

So here’s my simple, no-fluff framework to underwrite a rental property in under 30 minutes. Whether you’re a beginner or just looking to tighten your process, I hope this helps!

Step 1: Pull the Core Property Info (5 mins)

I grab the listing from the MLS, Zillow or Redfin and jot down:

• Asking price
• Estimated market rent (cross-check Rentometer + Craigslist/Zillow comps)
• Taxes, insurance, HOA (if any)
• Square footage and condition (rough rehab estimate)
• Year built, bed/baths, lot size

Asking price

Estimated market rent (cross-check Rentometer + Craigslist/Zillow comps)

Taxes, insurance, HOA (if any)

Square footage and condition (rough rehab estimate)

Year built, bed/baths, lot size

💡 Pro tip: Bookmark a few rent comp tools and create a deal template in Excel or Google Sheets to speed this up.

Step 2: Estimate Income & Expenses (10 mins)

Income:

• Monthly Rent: Estimate conservatively.
• Other income: Laundry, pet rent, storage? Optional but nice to add.

Monthly Rent: Estimate conservatively.

Other income: Laundry, pet rent, storage? Optional but nice to add.

Expenses (as % of rental income or fixed):

• Vacancy: 3–6%
• Maintenance: 5–8%
• CapEx: 5–8% (especially if roof, HVAC, etc. are aging)
• Management: 8–10% (even if self-managing, I budget this)
• Property Taxes & Insurance: Use actual or estimate based on comps. Taxes are public record on the county website.
• You'll also need P&I: A spreadsheet calculator can do the trick

Vacancy: 3–6%

Maintenance: 5–8%

CapEx: 5–8% (especially if roof, HVAC, etc. are aging)

Management: 8–10% (even if self-managing, I budget this)

Property Taxes & Insurance: Use actual or estimate based on comps. Taxes are public record on the county website.

You'll also need P&I: A spreadsheet calculator can do the trick

📈 Try not to be too conservative. This was a mistake I made at first and I could never find anything that penciled out!

Step 3: Run the Numbers (10 mins)

Now I plug everything into a simple cash flow calculator (BiggerPockets or my spreadsheet). I’m looking for:

• Monthly Cash Flow: Positive is a must, but I also want buffer. 
• Cash-on-Cash Return: Targeting 5-10%+ for rentals is usually a pretty good idea in this market.
• Total Return: All returns including appreciation and loan paydown.

Monthly Cash Flow: Positive is a must, but I also want buffer.

Cash-on-Cash Return: Targeting 5-10%+ for rentals is usually a pretty good idea in this market.

Total Return: All returns including appreciation and loan paydown.

If it’s a BRRRR or flip — I’d also:

• Estimate rehab costs
• Determine ARV
• Use the 70% Rule (or my own variation) to decide max allowable offer

Estimate rehab costs

Determine ARV

Use the 70% Rule (or my own variation) to decide max allowable offer

Step 4: Go/No-Go Decision (5 mins)

At this point, I ask:

• Do the numbers hit my criteria?
• Is it worth more time (contacting agent, running deeper comps, walking the property)?
• Can I make a strong offer with confidence?
• Are there some things I can do to make it work?

Do the numbers hit my criteria?

Is it worth more time (contacting agent, running deeper comps, walking the property)?

Can I make a strong offer with confidence?

Are there some things I can do to make it work?

If yes → I take the next step.
If no → Pass and move on. Time is money.

Real-World Example:

I recently looked at a Triplex listed for $450K.

• Total Rents: $4,750/month
• All-in expenses (with CapEx, PM, vacancy, etc.): $3,734
• Cash Flow: ~$1,017/mo
• Cash-on-Cash: ~8.65% on a 25% down loan

Total Rents: $4,750/month

All-in expenses (with CapEx, PM, vacancy, etc.): $3,734

Cash Flow: ~$1,017/mo

Cash-on-Cash: ~8.65% on a 25% down loan

🔍 Took 27 minutes

Final Thought:

This process isn’t perfect — but it gets me 80% of the way there fast. And that’s enough to separate the deals from the duds.

How do YOU underwrite your deals?
Got a favorite tool or spreadsheet you swear by?

Drop your tips (or questions) below 👇 Let’s compare systems.

Mason Vitalis · Answer

Great question! This is where an investor focused realtor can really come in handy, so I'll shamelessly plug my services haha. With access to the MLS I search for comparable properties sold within the last 90 days that match the after-repair features(bed/bath count, square footage, neighborhood, etc.). You can do this too to an extent on sites like Zillow or Realtor.com. I like to analyze conservatively because the renovation almost always seems to go over budget, so I like to have a buffer. On a BRRRR you'll want to make sure you can get all or at least most of your investment out after refinancing. It's also important to analyze the property as a rental like I did above with the ARV to make sure it's profitable after the reno. Hope this helps!

Thomas Adams · Answer

Super valuable.. how do you determine the ARV in the BRRRR case? Are you using a software or calculating it yourself somewhow?

Mason Vitalis · Answer

I did not analyze it as a section 8 investment. Just used Rentometer median rents. I didn't buy it but it's currently active on market, so the numbers are estimates. I included P&I in the total expenses for simplicity which was about $2109 on its own. Personally, I avoid using cap rate for residential multi because it doesn't account for financing or appreciation and isn't the best metric for owner occupant buyers which I focus on.

Jaycee Greene · Answer

@Mason Vitalis I agree that cap rates aren't applicable for house hacks, but I'd suggest going forward you mention that you're viewing it through a HH lens. Also, and perhaps contrary to how BP positions this, but P&I payments are excluded from the NOI calculation in traditional valuations.

Jaycee Greene · Answer

@Mason Vitalis I'm assuming this is a Section 8 property, is that correct? Those operating expenses ($3,734/month) are off the charts high. What's the cap rate, 2.75%?